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IBM 729

2008-03-06T18:16:38Z

RTC: Undid revision 196328499 by RTC (talk) Nope: according to the manual they did look identical

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|280px|A bank of IBM 729 tape drives.]]
[[Image:Tapesticker.jpg|thumb|Reel of tape showing beginning-of-tape reflective marker.]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. Part of the [[IBM 7 track]] family of tape units, it was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]].

==Data format==
The tape had [[IBM 7 track|seven parallel tracks]], six for data and one to maintain [[parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s (about 4,000,000 six-bit bytes).

The 729 series was superseded by [[9 track tape]] drives introduced with the IBM [[System/360]].

==Models==
In early development, the prototype 729 had two status lights labeled ''Select'' and ''Idle''. One day a vice president visited the lab and noticing this told the Engineers "That is not acceptable! IBM machines are NEVER idle!" The labels on the lights were quickly changed to ''Select'' and ''Ready''.
===729 I===
The IBM 729 I was introduced for the [[IBM 709]] and [[IBM 705|IBM 705 III]] computers, looked identical to the [[IBM 727]], and used [[vacuum tube]]s. The main improvement was the use of a dual gap head permitting write verify.

===729 II===
The IBM 729 II was introduced for the [[IBM 700/7000 series#IBM 7000 series, transistors, 1960s|IBM 7000 series]] computers, introducing a new cabinet style and [[transistor]]ized circuitry. Supported dual density (200, 556).

===729 III===
High speed (112.5 in/s) single density (556).
[[Image:Ibm-729v.jpg|thumb|An IBM 729 V at Deutsches Museum, Munich]]

===729 IV===
High speed (112.5 in/s) dual density (200, 556).

===729 V===
High density (800).

===729 VI===
High speed (112.5 in/s) high density (800).

==References==
* IBM 709 Data Processing System, Form A22-6501-0

==External links==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|729]]
[[Category:IBM 700/7000 series|Tape 729]]

IBM 729

2008-03-06T18:00:27Z

RTC: /* 729 I */

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|280px|A bank of IBM 729 tape drives.]]
[[Image:Tapesticker.jpg|thumb|Reel of tape showing beginning-of-tape reflective marker.]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. Part of the [[IBM 7 track]] family of tape units, it was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]].

==Data format==
The tape had [[IBM 7 track|seven parallel tracks]], six for data and one to maintain [[parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s (about 4,000,000 six-bit bytes).

The 729 series was superseded by [[9 track tape]] drives introduced with the IBM [[System/360]].

==Models==
In early development, the prototype 729 had two status lights labeled ''Select'' and ''Idle''. One day a vice president visited the lab and noticing this told the Engineers "That is not acceptable! IBM machines are NEVER idle!" The labels on the lights were quickly changed to ''Select'' and ''Ready''.
===729 I===
The IBM 729 I was introduced for the [[IBM 709]] and [[IBM 705|IBM 705 III]] computers, looked nearly identical to the [[IBM 727]], and used [[vacuum tube]]s. The main improvement was the use of a dual gap head permitting write verify.

===729 II===
The IBM 729 II was introduced for the [[IBM 700/7000 series#IBM 7000 series, transistors, 1960s|IBM 7000 series]] computers, introducing a new cabinet style and [[transistor]]ized circuitry. Supported dual density (200, 556).

===729 III===
High speed (112.5 in/s) single density (556).
[[Image:Ibm-729v.jpg|thumb|An IBM 729 V at Deutsches Museum, Munich]]

===729 IV===
High speed (112.5 in/s) dual density (200, 556).

===729 V===
High density (800).

===729 VI===
High speed (112.5 in/s) high density (800).

==References==
* IBM 709 Data Processing System, Form A22-6501-0

==External links==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|729]]
[[Category:IBM 700/7000 series|Tape 729]]

IBM 729

2008-03-06T17:51:16Z

RTC: /* Models */

IBM 729

2008-03-04T23:52:17Z

RTC: /* Models */

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|280px|A bank of IBM 729 tape drives.]]
[[Image:Tapesticker.jpg|thumb|Reel of tape showing beginning-of-tape reflective marker.]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. Part of the [[IBM 7 track]] family of tape units, it was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]].

==Data format==
The tape had [[IBM 7 track|seven parallel tracks]], six for data and one to maintain [[parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s (about 4,000,000 six-bit bytes).

The 729 series was superseded by [[9 track tape]] drives introduced with the IBM [[System/360]].

==Models==
In early development, the prototype 729 had two status lights labeled ''Select'' and ''Idle''. One day someone from management visited the lab and noticing this told the Engineers "That is not acceptable! IBM machines are NEVER idle!" The labels on the lights were quickly changed to ''Select'' and ''Ready''.
===729 I===
The IBM 729 I was introduced for the [[IBM 709]] and [[IBM 705|IBM 705 III]] computers, looked identical to the [[IBM 727]], and used [[vacuum tube]]s. The main improvement was the use of a dual gap head permitting write verify.

===729 II===
The IBM 729 II was introduced for the [[IBM 700/7000 series#IBM 7000 series, transistors, 1960s|IBM 7000 series]] computers, introducing a new cabinet style and [[transistor]]ized circuitry. Supported dual density (200, 556).

===729 III===
High speed (112.5 in/s) single density (556).
[[Image:Ibm-729v.jpg|thumb|An IBM 729 V at Deutsches Museum, Munich]]

===729 IV===
High speed (112.5 in/s) dual density (200, 556).

===729 V===
High density (800).

===729 VI===
High speed (112.5 in/s) high density (800).

==References==
* IBM 709 Data Processing System, Form A22-6501-0

==External links==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|729]]
[[Category:IBM 700/7000 series|Tape 729]]

Weltraumzeitalter

2008-02-15T23:26:47Z

RTC: /* Interactive Media */

[[Image:Space_Shuttle_Columbia_launching.jpg|thumb|The [[Space Shuttle]] takes off on a manned mission to space.]]

The '''Space Age''' is a contemporary period encompassing the activities related to the [[Space Race]], [[space exploration]], space technology, and the cultural developments influenced by these events.

==Beginning==
The Space Age began with the development of several technologies that culminated on [[October 4]], [[1957]], with the launch of [[Sputnik 1]] by the [[Soviet Union]]. This was the world's first artificial satellite, orbiting the Earth in 98.1 minutes and weighting in at 83kg. The launch of Sputnik 1 ushered a new era of political, scientific and technological achievements that became known as the Space Age.

The Space Age was characterized by rapid development of new technology in a close race mainly between [[USA]] and the [[Soviet Union]]. Rapid advances were made in [[rocket]]ry, [[materials science]], [[computer]]s and many other areas. Much of the technology originally developed for space applications has been [[Spin-off|spun off]] and found other uses.

The Space Age reached its peak with the [[Apollo program]] which captured the imagination of much of the world's population. The landing of [[Apollo 11]] is an event watched by over 500 million people around the world and is widely recognized as one of the defining moments of the [[20th century]]. Since then and with the end of the space race due to the [[collapse of the Soviet Union]], public attention has largely moved to other areas.

During the [[1990]]s funding for space related programs fell sharply as the [[Soviet Union]] disintegrated and [[NASA]] no longer had any direct competition. Also, public perception of the dangers and cost of space exploration in the USA was greatly affected by the [[Challenger disaster]] in [[1986]].

Since then participation in space launches have increasingly widened to more governments and commercial interests. Since the [[1990]]s, the current period has more often been referred to as the [[Information Age]] rather than the Space Age, since space exploration and space-related technologies are no longer felt to be commonplace by significant portions of the public.

==Current period==

In the early 21st century, the [[Ansari X Prize]] competition was set up to help jump start [[private spaceflight]] which was won by [[Space Ship One]] in 2004, becoming the first spaceship not funded by a government agency.

Several countries now have space programs; from related technology ventures to full fledge space programs with launch facilities. There are many scientific and commercial satellites in use today, with a total of hundreds of [[satellite]]s in orbit and several countries have plans to send humans in space.

==Chronology of the Space Age==
[[Image:Luna3 farside.gif|thumb|right|200px|First view ever of the far side of the Moon (mosaic of original Luna 3 500mm lenses frames), taken by [[luna 3]] on [[October 7]], 1959.]]
* [[October 4]], [[1957]]. [[Sputnik 1]], the world's first artificial satellite is launched by the [[Soviet Union]].
* [[October 7 ]], [[1959]]. [[Luna 3]] takes the first pictures of the 'dark side of the moon' and transmits them back to Earth.
* [[April 12]], [[1961]]. [[Yuri Gagarin]] becomes the first man in [[Outer space|space]].
*[[March 18]], [[1965]]. [[Alexey Leonov]] makes the first [[Extra-vehicular activity|'spacewalk']] during the [[Voskhod 2]] mission.
* [[December 21]]-[[December 25|27]], [[1968]]. The crew of [[Apollo 8]] becomes the first humans to leave the Earth's influence, and orbit another world, the [[Moon]]. First spacecraft to perform a [[Trans Earth Injection]] (TEI) maneuver.
* [[July 20]], [[1969]]. [[Neil Armstrong]], commander of [[Apollo 11]], becomes the first [[human being]] to walk on the [[Moon]].
* [[April 19]], [[1971]]. [[Salyut 1]] is launched, becoming the first [[space station]].
* [[December 3]], [[1973]]. [[Pioneer 10]] was the first spacecraft to make direct observations of [[Jupiter]], and was the first spacecraft to travel through the asteroid belt.
* [[July 20]], [[1976]]. [[Viking 1]] lands on [[Mars]] and transmits pictures from the surface.
* [[April 12]], [[1981]]. The first reusable space ship, the [[Space Shuttle]] is launched for the first time.
* [[February 19]], [[1986]]. The first long duration [[space station]], [[Mir]], is launched. Staying in orbit for over 15 years, occupants set several records in human space endurance.
* [[February 14]], [[1990]]. [[Voyager 1]] takes the first [[photograph]] of the whole [[solar system]]. <ref>See [http://filer.case.edu/sjr16/advanced/20th_far_voyagers.html] under "Extended Mission" </ref>
* [[April 24]], [[1990]]. The first large [[space telescope]], the [[Hubble Space Telescope]] is launched into orbit.
* [[November 2]], [[2000]]. The [[Expedition 1|first resident crew]] enters the [[International Space Station]], a large space station designed as a [[human]] [[habitat]].

==Earlier spaceflights==

The Space Age might also be considered to have begun much earlier than October 4, 1957, because on [[October 3]], [[1942]], a German [[Aggregate series|A4]] rocket, a prototype version of the [[V-2 rocket]] program reached space, therefore becoming the first man-made object to enter [[outer space|space]], albeit only briefly. Since this flight was undertaken in secrecy, it wasn't public knowledge for many years afterwards. As well, the German launch, and the subsequent [[sounding rocket]] tests performed in both the USA and USSR during the late 1940s and early 1950s, were not considered significant enough for starting a new age, because they did not reach orbit. Having a rocket powerful enough to reach orbit, meant that a nation had the ability to place a payload anywhere on the planet, or to use another term, possess an [[inter-continental ballistic missile]]. The fact that nowhere on the planet was safe from a nuclear warhead is why the orbit standard is used to define when the space age started.<ref>{{cite book
| last =Schefter
| first = James
| authorlink =
| coauthors =
| title = The Race: The Uncensored Story of How America Beat Russia to the Moon
| publisher = [[Doubleday (publisher)|Doubleday]]
| date = [[1999]]
| location =[[New York, New York]]
| pages = pp.3-49
| url =
| doi =
| id =
| isbn = 0-385-49253-7 }}</ref>

==References==
<references/>
==See also==
*[[Space Exploration]]
*[[Space Race]]
*[[Spacecraft]]
*[[Human spaceflight]]
*[[Space probe]]
*[[Information Age]]
*[[Atomic Age]]
*[[Populuxe]] (space age design movement)

==Interactive Media==

*[http://www.nasa.gov/externalflash/SpaceAge/index.html NASA's 50th Anniversary of the Space Age & Sputnik - Interactive Media]

[[Category:American generations]]
[[Category:Space exploration]]
[[Category:Historical eras]]
[[Category:20th century]]
[[Category:1957 introductions]]

[[ar:عصر الفضاء]]
[[es:Era espacial]]
[[it:Era spaziale]]
[[ka:კოსმოსის ეპოქა]]
[[hu:Űrtörténelem]]

CDC 6600

2008-02-15T00:37:31Z

RTC: /* External links */

[[Image:Control Data 6600 mainframe.jpg|thumb|right|300px|A ''CDC 6600'' mainframe system console]]
The '''CDC 6600''' was a [[mainframe computer]] from [[Control Data Corporation]], first delivered in [[1964]]. It is generally considered to be the first successful [[supercomputer]], outperforming its fastest predecessor, [[IBM 7030 Stretch]], by about three times. It remained the world's fastest computer from 1964 to [[1969]], when it relinquished that status to its successor, the [[CDC 7600]].

The system organization of the CDC 6600 was used for the simpler (and slower) [[CDC 6400]], and later a version containing two 6400 processors known as the [[CDC 6500]]. These machines were instruction-compatible with the 6600, but ran slower due to a much simpler and more sequential processor design. The [[CDC 7600]] was originally to be compatible as well, starting its life as the CDC 6800, but during the design compatibility was dropped in favor of outright performance. The entire family is now referred to as the [[CDC 6000 series]]. The 7600 and 6600 were binary compatible, but the software developed in Sunnyvale was not compatible on the two machines.
==History and impact==
{{main|Control Data Corporation}}

CDC's first products were based on the machines designed at [[Engineering Research Associates|ERA]], which [[Seymour Cray]] had been asked to update after moving to CDC. After an experimental machine known as the '''Little Character''', they delivered the [[CDC 1604]], one of the first commercial [[transistor]]-based computers, and one of the fastest machines on the market. Management was delighted, and made plans for a new series of machines that were more tailored to business use; they would include instructions for character handling and record keeping for instance. Cray was not interested in such a project, and set himself the goal of producing a new machine that would be 50 times faster than the 1604. When asked to complete a detailed report on future plans at one and five years into the future, he wrote back that his five year goal was "to produce the largest computer in the world", and his one year plan "to be one-fifth of the way".

Taking his core team to new offices nearby the original CDC headquarters, they started to experiment with higher quality versions of the "cheap" transistors Cray had used in the 1604. After much experimentation they found that there was simply no way the [[germanium]]-based transistors could be run much faster than the 1604. In fact the "business machine" that management had originally wanted, now forming as the [[CDC 3000]] series, pushed them about as far as they could go. Cray then decided the solution was to work with the then-new [[silicon]]-based transistors from [[Fairchild Semiconductor]], which were just coming onto the market and offered dramatically improved switching performance.

During this period CDC grew from a startup to a large company. Cray became increasingly frustrated with what he saw as ridiculous management requirements. Things became considerably more tense in 1962 when the new CDC 3600 started to near production quality, and appeared to be exactly what management wanted, when they wanted it. Cray eventually told CDC's CEO, [[William Norris]] that something had to change, or he would leave the company. Norris felt he was too important to lose, and gave Cray the green light to set up a new lab wherever he wanted.

After a short search, Cray decided to return to his home town of [[Chippewa Falls, WI]], where he purchased a block of land and started up a new lab. Although this process introduced a fairly lengthy delay in the design of his new machine, once in the new lab things started to progress quickly. By this time the new transistors were becoming quite reliable, and modules built with them tended to work properly on the first try. Working with Jim Thornton, who was the system architect and the 'hidden genius' behind the 6600, the machine soon took form.

More than 100 CDC 6600's were sold over the machine's lifetime. Many of these went to various [[nuclear bomb]]-related labs, and quite a few found their way into university computing labs. Cray immediately turned his attention to its replacement, this time setting a goal of 10 times the performance of the 6600, delivered as the [[CDC 7600]]. The later [[CDC Cyber]] 70 and 170 computers were much like the CDC 6600.

==Description==
Typical machines of the era used a single complex [[Central processing unit|CPU]] to drive the entire system. A typical program would first load data into memory (often using pre-rolled library code), process it, and then write it back out. This required the CPUs to be fairly complex in order to handle the complete set of instructions they needed to run. A complex CPU implied a large CPU, introducing signalling delays while information flowed between the individual modules making it up. These delays set a maximum upper limit on performance, the machine could only operate at a cycle speed that allowed the signals time to arrive at the next module.

Cray took another approach. At the time, CPUs generally ran slower than the [[main memory]] they were attached to. For instance, a processor might take 15 cycles to multiply two numbers, while each memory access took only one or two. This meant there was a significant time where the main memory was idle. It was this idle time that the 6600 extracted.

Instead of trying to make the CPU handle all the tasks, the 6600's handled math and logic only. This resulted in a much smaller CPU, which in turn allowed it to operate at a higher clock speed. Combined with the faster switching speeds of the silicon transistors, the new CPU design would easily outperform anything then available. The new design ran at 10 MHz (100ns cycle), about ten times that of other machines on the market. Additionally the simple processor also made operations themselves faster; for instance, the CPU could complete a multiplication in ten cycles.

Of course, being simple, it wouldn't be able to do much, either. In order to handle all of the normal "housekeeping" tasks a typical CPU was asked to handle memory and [[input/output]] as well. Cray removed these instructions from the main CPU, and instead implemented them in a set of 10 simpler processors called PPs, or peripheral processing units. By allowing the CPU, PPs and I/O to operate in parallel, the design considerably improved the performance of the machine.

Of course this would also make the machine dramatically more expensive. Key to the 6600's design was to make the I/O processors, known as '''Peripheral Processors''' or ''PP''s, as simple as possible. The PPs were based on the simple 12-bit [[CDC 160A]], which ran much slower than the CPU, gathering up data and "squirting" it into main memory at high speed via dedicated hardware. To make up for their slow speed, the 6600 included ten PP's in total.

The machine as a whole operated in a fashion known as "'''barrel and slot'''", the "barrel" referring to the ten PP's, and the "slot" the main CPU. For any given slice of time, one PP was given control of the CPU, asking it to complete some task (if required). Control was then handed off to the next PP in the barrel. Programs were written, with some difficulty, to take advantage of the exact timing of the machine to avoid any "dead time" on the CPU. With the CPU running much faster than normal each memory access required ten of these faster cycles to complete, so by using ten PP's, each PP was guaranteed one memory access per machine cycle.

The 10 PP's were implemented "'''virtually'''" - there was CPU hardware only for a single PP. This CPU hardware was shared and operated on 10 PP register sets which represented each of the 10 PP "'''states'''" (like in modern [[temporal multithreading|multithreading]] processors). The "'''PP [[barrel processor |register barrel]]'''" would "'''rotate'''", with each PP register set presented to the "'''slot'''" which the actual PP CPU occupied. The shared CPU would execute all or some portion of a PP's instruction whereupon the barrel would rotate again, presenting the next PP's register set (state). Multiple rotations of the barrel were needed to complete an instruction. A complete barrel rotation occurred in 1000 nanoseconds (100 nanoseconds per PP), and an instruction could take from 1 to 5 rotations of the barrel to be completed, or more if it was a data transfer instruction.

The basis for the 6600 CPU is what we would today refer to as a [[RISC]] system, one in which the processor is tuned to do instructions which are comparatively simple and have limited and well defined access to memory. The philosophy of many other machines was toward using instructions which were complicated — for example, a single instruction which would fetch an operand from memory and add it to a value in a register. In the 6600, loading the value from memory would require one instruction, and adding it would require a second. While slower in theory due to the additional memory accesses, the PPs offloaded this expense. This simplification also forced programmers to be very aware of their memory accesses, and therefore code deliberately to reduce them as much as possible.

===The Central Processor (CP)===
The Central Processor (CP) and main memory of the 6400, 6500, and 6600 machines have a 60 bit word length. The reason for this choice is that 60 is the least common multiple of 2, 3, 4, 5, 6, 10, 12, and 15, all of which numbers figure{{huh|date=November 2007}} in either the architecture or the packaging of the system.

The Central Processor has eight general purpose 60-[[bit]] [[processor register|registers]] X0 through X7, eight 18-bit address registers A0 through A7, and eight 18-bit scratchpad registers B0 through B7 (typically used for array indexing, with B0 permanently set to zero). Additional registers used for bookkeeping (such as the [[Scoreboarding|scoreboard]] register) are not accessible to the programmer. Additional registers (such as RA and FL) can only be loaded through the [[operating system]]. The CP has no instructions for input and output, which are accomplished through Peripheral Processors (below). In keeping with the RISC "load/store" philosophy, there are no instructions to read or write from/to core memory. All memory accesses are performed through loading an address into the A registers; loading A1 through A5 with an address would cause the data word at that location to be read into the corresponding X register (X1 through X5), while loading an address into A6 or A7 would cause register X6 or X7 to be written out to memory at that address. (Registers X0 and A0 were not involved in load/store operations this way.) A separate hardware load/store unit handled the actual data movement independent of the operation of the instruction stream, allowing other operations to complete while memory was being accessed, which required (best case) eight cycles. In modern designs this sort of operation is normally supported directly by load/store instructions, which are given an explicit memory location to read or write, instead of the address registers used in the 6600. Floating-point operations were given pride of place in this [[Computer architecture|architecture]]: the CDC 6600 (and kin) stand virtually alone in being able to execute a 60-bit [[floating point]] multiplication in time comparable to that for a program branch.

The 6600 CP included 10 parallel functional units, allowing multiple instructions to be worked on at the same time. Today this is known as a [[superscalar]] design, while at the time it was simply "unique". The system read and decoded instructions from memory as fast as possible, generally faster than they could be completed, and fed them off to the units for processing. The units were:
*floating point multiply (2 copies)
*floating point divide
*floating point add
*"long" integer add
*incrementers (2 copies; performed memory load/store)
*shift
*boolean logic
*branch

Previously executed instructions went into an eight-word [[Pipeline (computing)|pipeline]] (officially called a "stack") kept in onboard CP registers. Since the 15-bit instructions were packed four to a word, the system could pick any one of up to 32 previous instructions to run depending on which units were free. The pipeline was always flushed by an unconditional jump; it was sometimes faster (and would never be slower) than a ''conditional'' jump. The system used a 10 megahertz clock, but used a four-phase signal to match the four-wide instructions, so the system could at times effectively operate at 40 MHz. A floating point multiplication took ten cycles, while a division took 29, and the overall performance considering memory delays and other issues was about 3 [[MFLOPS]]. Using the best available compilers, late in the machine's history, [[FORTRAN]] programs could expect to maintain about 0.5 MFLOPS.

===Memory organization===


User programs are restricted to use only a contiguous area of main memory. The portion of memory to which an executing program has access is controlled by the '''RA''' (Relative Address) and '''FL''' (Field Length) registers which are not accessible to the user program. When a user program tries to read or write a word in central memory at address '''a''', the processor will first verify that a is between 0 and FL-1. If it is, the processor accesses the word in central memory at address RA+a. This process is known as base-bound relocation; each user program sees core memory as a contiguous block words with length FL, starting with address 0; in fact the program may be anywhere in the physical memory. Using this technique, each user program can be moved ("relocated") in main memory by the operating system, as long as the RA register reflects its position in memory. A user program which attempts to access memory outside the allowed range (that is, with an address which is not less than FL) will trigger an interrupt, and will be terminated by the operating system. When this happens, the operating system may create a [[core dump]] which records the contents of the program's memory and registers in a file, allowing the developer of the program a means to know what happened. Note the distinction with [[virtual memory]] systems; in this case, the entirety of a process's addressable space must be in core memory, must be contiguous, and its size cannot be larger than the real memory capacity.

All but the earliest 10 [[CDC 6000 series]] machines could be configured with an optional Extended Core Storage (ECS) system. ECS was built from a different variety of core memory than was used in the central memory. This made it economical for it to be both larger and slower. The primary reason was that ECS memory was wired with only 2 wires per core (contrast with 4 for central memory), and also because it performed very wide transfers. A 6000 CPU could directly perform block memory transfers between a user's program and the ECS unit. Wide data paths were used, so this was a very fast operation. Memory bounds were maintained in a similar manner as central memory - with a RA/FL mechanism maintained by the operating system. ECS could be used for a variety of purposes, including containing user data arrays that were too large for central memory, holding often-used files, swapping, and even as a communication path in a multi-mainframe complex.

===Peripheral Processors (PPs)===
To handle the 'household' tasks which other designs put in the CPU, Cray included ten other processors, based partly on his earlier computer, the [[CDC 160A]]. These machines, called Peripheral Processors, or PPs, were full computers in their own right, but were tuned to performing [[Input/output|I/O]] tasks and running the operating system. One of the PP's was in overall control of the machine, including control of the program running on the main CPU, while the others would be dedicated to various I/O tasks—quite similarly to [[I/O channel]]s in [[IBM mainframe]]s of the time. When the program needed to perform some sort of I/O, it instead loaded a small program into one of these other machines and let it do the work. The PP would then inform the CPU when the task was complete with an interrupt.

Each PP included its own memory of 4096 12-bit words. This memory served for both for I/O buffering and program storage, but the execution units were shared by 10 PPs, in a configration called the [[Barrel processor|Barrel and slot]]. This meant that the execution units (the "slot") would execute one instruction cycle from the first PP, then one instruction cycle from the second PP, etc. in a round robin fashion. This was done both to reduce costs, and because access to CP memory required 10 PP clock cycles: when a PP accesses CP memory, the data is available next time the PP receives its slot time.

===Wordlengths, characters===
The central processor had 60-bit words, whilst the peripheral processors had 12-bit words. CDC used the term "byte" to refer to 12-bit entities used by peripheral processors; characters were 6-bit, and central processor instructions were either 15 bits, or 30 bits with a signed 18-bit address field, the latter allowing for a directly addressable memory space of 128K words of central memory (converted to modern terms, with 8-bit bytes, this is 0.94 megabytes). The signed nature of the address registers limited an individual program to 128K words. (Later CDC 6000-compatible machines could have 256K or more words of central memory, budget permitting, but individual user programs were still limited to 128K words of CM.) Central processor instructions started on a word boundary when they were the target of a jump statement or subroutine return jump instruction, so no-operations were sometimes required to fill out the last 15, 30 or 45 bits of a word.

The 6-bit characters, in an encoding called [[display code]], could be used to store up to 10 characters in a word. They permitted a character set of 64 characters, which is enough for all upper case letters, digits, and some punctuation. Certainly, enough to write [[FORTRAN]], or print financial or scientific reports. There were actually two variations of the [[display code]] character sets in use, 64-character and 63-character. The 64-character set had the disadvantage that two consecutive ':' (colon) characters might be interpreted as the end of a line if they fell at the end of a 10-byte word. A later variant, called 6/12 [[display code]], was also used in the KRONOS and [[NOS (Software)|NOS]] timesharing systems to allow full use of the [[ASCII]] character set in a manner somewhat compatible with older software.

With no byte addressing instructions at all, code had to be written to pack and shift characters into words. The very large words, and comparatively small amount of memory, meant that programmers would frequently economize on memory by packing data into words at the bit level.

It is interesting to note that due to the large word size, and with 10 characters per word, it was often faster to process words full of characters at a time - rather than unpacking/processing/repacking them. For example, the CDC [[COBOL]] compiler was actually quite good at processing decimal fields using this technique. These sorts of techniques are now commonly used in the 'multi-media' instructions of current processors.

===Physical design===
The machine was built in a plus-sign-shaped cabinet with a pump and heat exchanger in the outermost 18 inches of each of the 4 arms. Cooling was done with [[Freon]] circulating within the machine and exchanging heat to an external chilled water supply. Each arm could hold 4 chassis, each about 8 inches thick, hinged near the center, and opening a bit like a book. The intersection of the "plus" was filled with cables which interconnected the chassis. The chassis were numbered from 1 (containing all 10 PPUs and their memories, as well as the 12 rather minimal I/O channels) to 16. The main memory for the CPU was spread over many of the chassis. In a system with only 64K words of main memory, one of the arms of the "plus" was omitted.

The logic of the machine was packaged into modules about 2.5 inches square and about an inch thick. Each module had a connector (roughly 20 pins in each of 2 vertical rows) on one edge, and 6 test points on the opposite edge. The module was placed between two aluminum cold plates to remove heat. The module itself consisted of two parallel printed circuit boards, with components mounted either on one of the boards or between the two boards. This provided a very dense, if somewhat difficult to repair, package with good heat removal that was known as [[Cordwood construction#Other meanings|cordwood packaging]].

==Operating system and programming==

If there was a sore point with the 6600 it was the [[operating system]] support, which took entirely too long to work out.

The machines originally ran a very simple [[batch processing|job-control]] system known as '''COS''', the '''''C'''hippewa '''O'''perating '''S'''ystem'', which was quickly "thrown together" based on the earlier [[CDC 3000]] operating system in order to have something running to test the systems for delivery. However the machines were intended to be delivered with a much more powerful system known as '''SIPROS''', for '''''SI'''multaneous '''PR'''ocessing '''O'''perating '''S'''ystem'', which was being developed at the company's System Sciences Division in [[Los Angeles]]. Customers were impressed with SIPROS's feature list, and many had SIPROS written into their delivery contracts.

SIPROS turned out to be a major fiasco. Development timelines continued to slip, costing CDC major amounts of profit in the form of delivery delay penalties. After several months of waiting with the machines ready to be shipped, the project was eventually cancelled. Luckily the programmers who had worked on COS had little faith in SIPROS (likely due largely to [[not invented here]] syndrome) and had continued working on it.

[[Operating system development]] then split into two camps. The CDC-sanctioned evolution of COS was undertaken at the Sunnyvale (California) software development lab. Many customers eventually took delivery of their systems with this software, then known as '''[[SCOPE (software)|SCOPE]]''' ('''S'''upervisory '''C'''ontrol '''O'''f '''P'''rogram '''E'''xecution) (Some Control Data Field Engineers used to refer to SCOPE as Sunnyvale's Collection Of Programming Errors) version 1 was, essentially, dis-assembled COS; SCOPE version 2 included new device and file system support; SCOPE version 3 included permanent file support, EI/200 remote batch support, and INTERCOM [[time sharing]] support. SCOPE always had significant reliability and maintainability issues.

The underground evolution of COS took place at the Arden Hills (Minnesota) assembly plant. '''MACE''' ('''M'''ansfield '''A'''nd '''C'''ahlander '''E'''xecutive) was written largely by a single programmer in the off-hours when machines were available. Its feature set was essentially the same as COS and SCOPE 1. It retained the earlier COS file system, but made significant advances in code modularity to improve system reliability and adaptiveness to new storage devices. MACE was never an official product, although many customers were able to wrangle a copy from CDC.

MACE was later used as the basis of '''[[KRONOS]]''', named after the [[Chronos|Greek god of time]]. The main marketing reason for its adoption was the development of its TELEX [[time sharing]] feature and its BATCHIO remote batch feature. KRONOS continued to use the COS/SCOPE 1 file system with the addition of a permanent file feature.

An attempt to unify the operating system products SCOPE and KRONOS produced '''[[NOS (Software)|NOS]]''', the '''''N'''etwork '''O'''perating '''S'''ystem''. NOS was ''the'' operating system for all CDC machines, a fact CDC promoted heavily. Many SCOPE customers remained software-dependent on the SCOPE architecture, so CDC simply renamed it [[NOS/BE]] (Batch Environment), and were able to claim that everyone was thus running NOS. In practice, it was far easier to modify the KRONOS code base to add SCOPE features than the reverse.

The assembly plant environment also produced other operating systems which were never intended for customer use. These included engineering tools SMM, for hardware testing; and KALEIDOSCOPE, for software [[smoke testing|smoke-testing]], another commonly used tool for CDC Field Engineers during testing was MALET (Maintenance Application Language for Equipment Testing), which was used to stress test components and devices after repairs and/or servicing by engineers (testing conditions often used hard disk packs and magnetic tapes which were deliberately marked with errors to determine if the errors would be detected by MALET and the engineer).

==Emulation==
[[Desktop CYBER]] emulates the CDC 6400 and various CDC CYBER mainframes in software running on modern desktop PCs.

==References==
*Grishman, Ralph (1974). ''Assembly Language Programming for the Control Data 6000 Series and the Cyber 70 Series''. New York, NY: Algorithmics Press. [http://computer-refuge.org/bitsavers/pdf/cdc/6x00/books/Grishman_CDC6000AsmLangPgmg.pdf]
*[http://ed-thelen.org/comp-hist/CDC-6600-R-M.html#TOC/ CONTROL DATA 6400/6500/6600 COMPUTER SYSTEMS Reference Manual]
*Thornton, J. (1963). ''Considerations in Computer Design - Leading up to the Control Data 6600'' [http://computer-refuge.org/bitsavers/pdf/cdc/6x00/thornton_6600_paper.pdf]
*Thornton, J. (1970). ''Design of a Computer -- The Control Data 6600''. Glenview, IL: Scott, Foresman and Co. [http://computer-refuge.org/bitsavers/pdf/cdc/6x00/books/DesignOfAComputer_CDC6600.pdf]

==See also==
* [[CDC 6000 series]]

==External links==
*[http://research.microsoft.com/~gbell/Computer_Structures__Readings_and_Examples/00000509.htm Parallel operation in the Control Data 6600, James Thornton]
*[http://research.microsoft.com/users/gbell/craytalk/sld001.htm Presentation of the CDC 6600 and other machines designed by Seymour Cray] – by C. [[Gordon Bell]] of Microsoft Research (formerly of DEC)
*[http://members.iinet.net.au/~tom-hunter/ Emulator of a "typical" CDC CYBER 6600, 7x, 17x based system]
[[Category:CDC hardware|6600]]
[[Category:Supercomputers]]
[[Category:1964 introductions]]

[[es:CDC 6600]]
[[it:CDC 6600]]
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[[fi:CDC 6600]]

IBM 7330

2007-12-07T23:45:28Z

RTC:

The '''IBM 7330 Magnetic Tape Unit''' was IBM's low cost [[magnetic tape|tape]] mass storage system through the [[1960s]]. Part of the [[IBM 7 track]] family of tape units, it was used mostly on [[IBM 1400 series|1400]] series computers. The 7330 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter.

==Data format==
The tape had [[IBM 7 track|seven parallel tracks]], six for data and one to maintain [[parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s (about 4,000,000 six-bit bytes).

Low speed (36 in/s) dual density (200, 556).

==External links==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|7330]]
[[Category:IBM 700/7000 series|Tape 7330]]

IBM 7330

2007-12-07T23:38:51Z

RTC: ←Created page with 'The '''IBM 7330 Magnetic Tape Unit''' was IBM's low cost tape mass storage system through the 1960s. Part of the IBM 7 track family of ta...'

The '''IBM 7330 Magnetic Tape Unit''' was IBM's low cost [[magnetic tape|tape]] mass storage system through the [[1960s]]. Part of the [[IBM 7 track]] family of tape units, it was used mostly on [[IBM 1400 series|1400]] series computers. The 7330 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. Unlike most other IBM tape drives, the 7330 lacked the long vacuum columns and operated a very low speed.

==Data format==
The tape had [[IBM 7 track|seven parallel tracks]], six for data and one to maintain [[parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s (about 4,000,000 six-bit bytes).

Low speed (TBD in/s) dual density (200, 556).

==External links==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|7330]]
[[Category:IBM 700/7000 series|Tape 7330]]

IBM 729

2007-12-06T18:16:31Z

RTC: /* 729 III */

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|280px|A bank of IBM 729 tape drives.]]
[[Image:Tapesticker.jpg|thumb|Reel of tape showing beginning-of-tape reflective marker.]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. Part of the [[IBM 7 track]] family of tape units, it was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]].

==Data format==
The tape had [[IBM 7 track|seven parallel tracks]], six for data and one to maintain [[parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s (about 4,000,000 six-bit bytes).

The 729 series was superseded by [[9 track tape]] drives introduced with the IBM [[System/360]].

==Models==
===729 I===
The IBM 729 I was introduced for the [[IBM 709]] and [[IBM 705|IBM 705 III]] computers, looked identical to the [[IBM 727]], and used [[vacuum tube]]s. The main improvement was the use of a dual gap head permitting write verify.

===729 II===
The IBM 729 II was introduced for the [[IBM 700/7000 series#IBM 7000 series, transistors, 1960s|IBM 7000 series]] computers, introducing a new cabinet style and [[transistor]]ized circuitry. Supported dual density (200, 556).

===729 III===
High speed (112.5 in/s) single density (556).
[[Image:Ibm-729v.jpg|thumb|An IBM 729 V at Deutsches Museum, Munich]]

===729 IV===
High speed (112.5 in/s) dual density (200, 556).

===729 V===
High density (800).

===729 VI===
High speed (112.5 in/s) high density (800).

==References==
* IBM 709 Data Processing System, Form A22-6501-0

==External links==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|729]]
[[Category:IBM 700/7000 series|Tape 729]]

IBM 729

2007-11-29T03:03:08Z

RTC: /* External links */

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|280px|A bank of IBM 729 tape drives.]]
[[Image:Tapesticker.jpg|thumb|Reel of tape showing beginning-of-tape reflective marker.]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. Part of the "[[IBM 7 Track]]" family of tape units, it was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]].

==Data format==
The tape had [[IBM 7 Track|seven parallel tracks]], six for data and one to maintain [[parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. (709 manual p. 20) Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s (about 4,000,000 six-bit bytes).

The 729 series was superseded by [[9 track tape]] drives introduced with the IBM [[System/360]].

==Models==
===729 I===
The IBM 729 I was introduced for the [[IBM 709]] and [[IBM 705|IBM 705 III]] computers, looked identical to the [[IBM 727]], and used [[vacuum tube]]s. The main improvement was the use of a dual gap head permitting write verify.

===729 II===
The IBM 729 II was introduced for the [[IBM 700/7000 series#IBM 7000 series, transistors, 1960s|IBM 7000 series]] computers, introducing a new cabinet style and [[transistor]]ized circuitry. Supported dual density (200, 556).

===729 III===
High speed (112.5 in/s) single density (556).
[[Image:Ibm-729v.jpg|thumb|An Ibm 729V at Deutsches Museum, Munich]]
===729 IV===
High speed (112.5 in/s) dual density (200, 556).

===729 V===
High density (800).

===729 VI===
High speed (112.5 in/s) high density (800).

==References==
* IBM 709 Data Processing System, Form A22-6501-0

==External links==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|729]]
[[Category:IBM 700/7000 series|Tape 729]]

Weltraumzeitalter

2007-08-01T16:04:25Z

RTC: /* Beginning */ byp redirs

[[Image:Space_Shuttle_Columbia_launching.jpg|thumb|The [[Space Shuttle]] takes off on a manned mission to space.]]

The '''Space Age''' is a contemporary period encompassing the activities related to the [[space race]], [[space exploration]], space technology, and the cultural developments influenced by these events.

==Beginning==
The Space Age began with the development of several technologies that culminated on [[October 4]], [[1957]], with the launch of [[Sputnik 1]] by the [[Soviet Union]]. This was the world's first artificial satellite, orbiting the Earth in 98.1 minutes and weighting in at 83kg. The launch of Sputnik 1 ushered a new era of political, scientific and technological achievements that became known as the Space Age.

The Space Age was characterized by rapid development of new technology in a close race mainly between [[USA]] and the [[Soviet Union]]. Rapid advances were made in [[rocket]]ry, [[materials science]], [[computer]]s and many other areas. Much of the technology originally developed for space applications has been [[Spin-off|spun off]] and found other uses.

The Space Age reached its peak with the [[Apollo program]] which captured the imagination of much of the world's population. The landing of [[Apollo 11]] is an event watched by over 500 million people around the world and is widely recognized as one of the defining moments of the [[20th century]]. Since then and with the end of the space race due to the [[collapse of the Soviet Union]], public attention has largely moved to other areas.

During the [[1990]]s funding for space related programs fell sharply as the [[Soviet Union]] disintegrated and [[NASA]] no longer had any direct competition. Also, public perception of the dangers and cost of space exploration in the USA was greatly affected by the [[Challenger disaster]] in [[1986]].

Since then participation in space launches have increasingly widened to more governments and commercial interests. Since the [[1990]]s, the current period has more often been referred to as the [[Information Age]] rather than the Space Age, since space exploration and space-related technologies are felt to be commonplace by significant portions of the public.

==Current period==

In the early 21st century, the [[Ansari X Prize]] competition was set up to help jump start [[private spaceflight]] which was won by [[Space Ship One]] in 2004, becoming the first spaceship not funded by a government agency.

Several countries now have space programs; from related technology ventures to full fledge space programs with launch facilities. There are many scientific and commercial satellites in use today, with a total of hundreds of [[satellite]]s in orbit and several countries have plans to send humans in space.

==Major events==
[[Image:Luna3 farside.gif|thumb|right|200px|First view ever of the far side of the Moon (mosaic of original Luna 3 500mm lenses frames), taken by [[luna 3]] on [[October 7]], 1959.]]
* [[October 4]], [[1957]]. [[Sputnik 1]], the world's first artificial satellite is launched by the [[Soviet Union]].
* [[October 7 ]], [[1959]]. [[Luna 3]] takes the first pictures of the 'dark side of the moon' and transmits them back to Earth.
* [[April 12]], [[1961]]. [[Yuri Gagarin]] becomes the first man in [[Outer space|space]].
*[[March 18]], [[1965]]. [[Alexey Leonov]] makes the first [[Extra-vehicular activity|'spacewalk']] during the [[Voskhod 2]] mission.
* [[December 21]]-[[December 27|27]], [[1968]]. The crew of [[Apollo 8]] becomes the first humans to leave the Earth's influence, and orbit another world, the [[Moon]]. First spacecraft to perform a [[Trans Earth Injection]] (TEI) maneuver.
* [[July 20]], [[1969]]. [[Neil Armstrong]], commander of [[Apollo 11]], becomes the first person to walk on the [[Moon]].
* [[April 19]], [[1971]]. [[Salyut 1]] is launched, becoming the first [[space station]].
* [[December 3]], [[1973]]. [[Pioneer 10]] was the first spacecraft to make direct observations of [[Jupiter]], and was the first spacecraft to travel through the asteroid belt.
* [[July 20]], [[1976]]. [[Viking 1]] lands on [[Mars]] and transmits pictures from the surface.
* [[April 12]], [[1981]]. The first reusable space ship, the [[Space Shuttle]] is launched for the first time.
* [[February 19]], [[1986]]. The first long duration [[space station]], [[Mir]], is launched. Staying in orbit for over 15 years, occupants set several records in human space endurance.
* [[February 14]], [[1990]]. [[Voyager 1]] takes the first [[photograph]] of the whole [[solar system]]. <ref>See [http://filer.case.edu/sjr16/advanced/20th_far_voyagers.html] under "Extended Mission" </ref>
* [[April 24]], [[1990]]. The first large space telescope, the [[Hubble Space Telescope]] is launched into orbit.
* [[November 2]], [[2000]]. The [[Expedition 1|first resident crew]] enters the [[International Space Station]], a large space station designed as a [[human]] [[habitat]].

==Earlier spaceflights==

The Space Age might also be considered to have begun much earlier than October 4, 1957, because on [[October 3]], [[1942]], a German [[Aggregate series|A4]] rocket, a prototype version of the [[V-2 rocket]] program reached space, therefore becoming the first man-made object to enter [[outer space|space]], albeit only briefly. Since this flight was undertaken in secrecy, it wasn't public knowledge for many years afterwards. As well, the German launch, and the subsequent [[sounding rocket]] tests performed in both the USA and USSR during the late 1940s and early 1950s, were not considered significant enough for starting a new age, because they did not reach orbit. Having a rocket powerful enough to reach orbit, meant that a nation had the ability to place a payload anywhere on the planet, or to use another term, possess an [[inter-continental ballistic missile]]. The fact that nowhere on the planet was safe from a nuclear warhead is why the orbit standard is used to define when the space age started.<ref>{{cite book
| last =Schefter
| first = James
| authorlink =
| coauthors =
| title = The Race: The Uncensored Story of How America Beat Russia to the Moon
| publisher = [[Doubleday]]
| date = [[1999]]
| location =[[New York, New York]]
| pages = pp.3-49
| url =
| doi =
| id =
| isbn = 0-385-49253-7 }}</ref>

==References==
<references/>
==See also==
*[[Space Exploration]]
*[[Space Race]]
*[[Spacecraft]]
*[[Human spaceflight]]
*[[Space probe]]
*[[Information Age]]
*[[Atomic Age]]
*[[Populuxe]] (space age design movement)

[[Category:American generations]]
[[Category:Space exploration]]
[[Category:Historical eras]]
[[Category:20th century eras]]

[[ar:عصر الفضاء]]
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[[it:Era spaziale]]
[[hu:Űrtörténelem]]

Projekt Athena

2007-07-31T17:33:56Z

RTC: byp redir

{{Expand|date=January 2007}}

'''Project Athena''' was a joint project of [[Massachusetts Institute of Technology|MIT]], [[Digital Equipment Corporation]], and [[IBM]]. It was launched in [[1983]], and research and development ran through [[June 30]], [[1991]], eight years after it began. The goals were to create a computing environment that would scale up to 10,000 workstations (like [[VAX]]) and accommodate heterogeneous hardware, yet be "coherent". This concept meant that a user could go to any workstation and access any files or applications without finding major differences in the user interface and service delivery, just like browsing the Internet today.

The project spawned many technologies that are widely used today, such as the [[X Window System]] and [[Kerberos (protocol)|Kerberos]]. Amongst the other technologies developed for Project Athena were the [[Xaw]] [[widget set]], [[Zephyr protocol|Zephyr Notification Service]] (which was the first [[instant messaging]] service), and the [[Hesiod (name service)|Hesiod]] name and directory service.

The [[X Window System]] originated as a joint project of Project Athena and MIT's [[Laboratory for Computer Science]], and was used by Athena.

When Project Athena ended in 1991, the computing environment was renamed to the Athena system, and is still used by many in the MIT community through the computer clusters scattered around the campus, despite the increasing popularity of laptops and ubiquity of wireless internet on campus.

[[Pixar Animation Studios]], the computer graphics and animation company (then the [[Lucasfilm]] Computer Graphics Project, now owned by Walt Disney Pictures), used most of the first fifty Project Athena systems before they went into general use rendering [[The Adventures of André and Wally B.]].

[[Iowa State]] runs an implementation of Athena named 'Project Vincent', named after [[John Vincent Atanasoff]], the inventor of the [[Atanasoff–Berry Computer]].

[[North Carolina State University]] also runs a variation of Athena named 'Eos/Unity'

[[Carnegie Mellon University]] runs a similar system called [[Andrew Project|Project Andrew]] which spawned [[Andrew File System|AFS]], Athena's current filesystem.

[[University of Maryland College Park]] also runs a variation of Athena named 'Project Glue'.

== References ==
* Treese, G. Winfield, [http://www.mirror.ac.uk/mirror/athena-dist.mit.edu/pub/ATHENA/usenix/athena_changes.PS Berkeley UNIX on 1000 Workstations: Athena Changes to 4.3 BSD] ''USENIX Association'', February 1988.
* Arfman, J. M.; Roden, Peter. [http://www.research.ibm.com/journal/sj/313/ibmsj3103I.pdf Project Athena: Supporting distributed computing at MIT] ''IBM Systems Journal'' Volume 31, Number 3, 1992.
* Champine, George (1991). ''MIT Project Athena: A Model for Distributed Campus Computing'', Digital Press, ISBN 1-55558-072-6.
* Avril, C. R.; Orcutt, Ron L. Athena: MIT's Once and Future Distributed Computing Project, ''Information Technology Quarterly'' (Fall 1990).
* Athena at MIT (mit.edu) [http://web.mit.edu/is/topics/athena/]

== External links ==
* [http://web.mit.edu/ist/topics/athena/ Athena at MIT]

{{MITtemplate}}

[[Category:Massachusetts Institute of Technology]]
[[Category:X Window System|Athena, Project]]
[[Category:Software Projects]]

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[[zh:雅典娜工程]]

Bau des World Trade Centers

2007-07-12T03:28:22Z

RTC: /* Structural design */

{{for|the post-9/11 rebuilding and ongoing construction at the World Trade Center site|World Trade Center site}}
[[Image:World trade center new york city construction flickr.png|thumb|right|250px|View of the World Trade Center's construction from across the [[Hudson River]]]]
The '''building of the [[World Trade Center]]''' started as a post-[[World War II]] [[urban renewal]] project, spearheaded by [[David Rockefeller]], to help revitalize [[Lower Manhattan]]. The project was developed by the [[Port Authority of New York and New Jersey]], which hired architect [[Minoru Yamasaki]] who came up with the specific idea for twin towers. After extensive negotiations, the [[New Jersey]] and [[New York|New York State]] governments, which oversee the Port Authority, agreed to support the World Trade Center project at the [[Radio Row]] site on the lower-west side of [[Manhattan]]. To make the agreement acceptable to New Jersey, the Port Authority agreed to take over the bankrupt Hudson & Manhattan Railroad (renamed as [[Port Authority Trans-Hudson|PATH]]), which brought commuters from New Jersey to the Lower Manhattan site.

The towers were designed as framed tube structures, which provided tenants with open floor plans, uninterrupted by columns or walls. This was accomplished using numerous closely-spaced perimeter columns to provide much of the strength to the structure, along with gravity load shared with the core columns. The [[elevator]] system, which made use of [[sky lobby|sky lobbies]] and a system of express and local elevators, allowed substantial floor space to be freed up for use as office space by making the structural core smaller. The design and construction of the World Trade Center twin towers involved many other innovative techniques, such as the [[slurry wall]] for digging the [[Foundation (architecture)|foundation]], and [[wind tunnel]] experiments. Construction of the World Trade Center's North Tower began in August 1968, and the South Tower in 1969. Extensive use of prefabricated components helped to speed up the construction process. The first tenants moved into the North Tower in December 1970 and into the South Tower in January 1972. Four other low-level buildings were constructed as part of the World Trade Center in the 1970s, and a [[7 World Trade Center|seventh]] building was constructed in the mid-1980s.

==Planning==
In 1942, [[Austin J. Tobin]] became the Executive Director of the [[Port Authority of New York and New Jersey|Port Authority]], beginning a 30-year career during which he oversaw the planning and development of the World Trade Center.<ref name="Doig-chap1">{{cite book |last=Doig |first=Jameson W. |title=Empire on the Hudson |year=2001 |publisher=Columbia University Press |chapter=Chapter 1}}</ref> The concept of establishing a "[[World Trade Center (disambiguation)|world trade center]]" was conceived during the post-[[World War II]] period, when the [[United States]] thrived economically and international trade was increasing. In 1946, the [[New York State Legislature]] passed a bill that called for a "world trade center" to be established.<ref name="nyt-07061946">{{cite news |title=Dewey Picks Board for Trade Center |publisher=The New York Times |date=July 6, 1946}}</ref> The World Trade Corporation was set up, and a board was appointed by New York Governor [[Thomas E. Dewey]] to develop plans for the project.<ref name="nyt-07061946"/> Architect [[John Eberson]] and his son Drew devised a plan that included 21 buildings over a ten-block area, at an estimated cost of $150 million.<ref>{{cite news |title=Plans are Tabled for Trade Center |author=Crisman, Charles B. |publisher=The New York Times |date=November 10, 1946}}</ref> In 1949, the World Trade Corporation was dissolved by the New York State Legislature, and plans for a "world trade center" were put on hold.<ref>{{cite news |title=Lets Port Group Disband, State Senate for Dissolution of World Trade Corporation |publisher=The New York Times |date=March 11, 1949}}</ref>

===Original plans===
[[Image:East-side-wtc.png|thumb|right|300px|Architect's model for the proposed World Trade Center on the East River]]
During the post-war period, economic growth was concentrated in [[Midtown Manhattan]], in part stimulated by the [[Rockefeller Center]], which was developed in the 1930s. Meanwhile, Lower Manhattan was left out of the [[Boom and bust|economic boom]]. One exception was the construction of [[One Chase Manhattan Plaza]] in the [[Financial District, Manhattan|Financial District]], by [[David Rockefeller]], who led [[urban renewal]] efforts in Lower Manhattan.<ref name="Gillespie-chap1">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |chapter=Chapter 1 |publisher=Rutgers University Press}}</ref> In 1958, Rockefeller established the Downtown-Lower Manhattan Association (DLMA), which commissioned [[Skidmore, Owings and Merrill]] to draw up plans for revitalizing [[Lower Manhattan]]. The plans, made public in 1960, called for a World Trade Center to be built on a 13 [[acre]] (5.25 [[Hectare|ha]]) site along the [[East River]], from [[Old Slip]] to [[Fulton Street (Manhattan)|Fulton Street]] and between [[Water Street (Manhattan)|Water Street]] and [[South Street (Manhattan)|South Street]].<ref name="Levinson">{{cite book|last=Levinson |first=Leonard Louis| title=Wall Street| year=1961| publisher=Ziff Davis Publishing| location=New York| page=346}}</ref><ref name="nyt-01271960">{{cite news |title=A World Center of Trade Mapped Off Wall Street |date=January 27, 1960 |publisher=The New York Times |author=Grutzner, Charles}}</ref> The complex would include a 900 [[Foot (unit of length)|foot]] (275 [[Metre|m]]) long [[Convention center|exhibition hall]], and a 50-70 story building, with some of its upper floors used as a hotel.<ref>{{cite book |title=Men of Steel: The Story of the Family That Built the World Trade Center |author=Koch, Karl III |publisher=Three Rivers Press |year=2002 |pages=p. 173}}</ref> Other amenities would include a theater, shops, and restaurants.<ref name="dlma-plan">{{cite news |title=Text of Trade Center Report by the Downtown-Lower Manhattan Association |publisher= The New York Times |date=January 27, 1960}}</ref> The plan also called for a new [[security (finance)|securities]] exchange building, which the Downtown-Lower Manhattan Association hoped would house the [[New York Stock Exchange]].<ref name="nyt-01271960"/>

David Rockefeller suggested that the Port Authority would be a logical choice for taking on the project.<ref name="nyt-01271960"/> Rockefeller argued that the Trade Center would provide great benefits in facilitating and increasing volume of international commerce coming through the Port of New York.<ref name="dlma-plan"/> Given the importance of [[New York City]] in global commerce, Port Authority director Austin J. Tobin remarked that the proposed project should be ''the'' World Trade Center, and not just ''a'' "world trade center".<ref>{{cite news |title=Tobin Says Proposed Center Should Be World's Best |publisher=The New York Times |date=May 5, 1960}}</ref> After a year-long review of the proposal, the Port Authority formally backed the project on [[March 11]] [[1961]].<ref>{{cite news |title=355 Million World Trade Center Backed by Port Authority Study |publisher=The New York Times |date=March 12, 1961}}</ref>

===Agreement===
[[Image:Wtc locator map.png|thumb|right|300px|Location of World Trade Center and originally proposed site]]
The States of New York and New Jersey also needed to approve the project, given their control and oversight role of the Port Authority. Objections to the plan came from [[New Jersey]] Governor [[Robert B. Meyner]], who resented that [[New York]] would be getting this $335 million project.<ref name="Gillespie-chap1"/> Meanwhile, ridership on New Jersey's [[Hudson and Manhattan Railroad]] (H&M) had declined substantially from a high of 113 million riders in 1927 to 26 million in 1958, after new automobile tunnels and bridges opened across the [[Hudson River]].<ref>{{cite book |title=Rails Under the Mighty Hudson |author=Cudahy, Brian J. |publisher=Fordham University Press |year=2002 |pages=p. 56}}</ref> Towards the end of 1961, negotiations with outgoing New Jersey Governor Meyner regarding the World Trade Center project reached a stalemate. In December 1961, Tobin met with newly elected New Jersey Governor [[Richard J. Hughes]], and made a proposal to shift the World Trade Center project to a west side site where the [[Hudson Terminal]] was located.<ref name="nyt-1961dec29">{{cite news |title=Port Unit Backs Linking of H&M and Other Lines |author=Grutzner, Charles |publisher=The New York Times |date=December 29, 1961}}</ref> In acquiring the Hudson & Manhattan Railroad, the Port Authority would also acquire the Hudson Terminal and other buildings which were deemed obsolete.<ref name="nyt-1961dec29"/> On [[January 22]] [[1962]], the two states reached an agreement to allow the Port Authority to take over the railroad and to build the World Trade Center on Manhattan's lower west side.<ref>{{cite news |title=2 States Agree on Hudson Tubes and Trade Center |author=Wright, George Cable |date=January 23, 1962 |publisher=The New York Times}}</ref> The shift in location for the World Trade Center to a site more convenient to New Jersey, together with Port Authority acquisition of the H&M Railroad, brought New Jersey to agreement in support of the World Trade Center project.

===Controversy===
Even once the agreement between the states of New Jersey, New York, and the Port Authority was finalized, the World Trade Center plan faced continued controversy. The site for the World Trade Center was the location of [[Radio Row]], which was home to hundreds of commercial and industrial tenants, property owners, small businesses, and approximately 100 residents.<ref name="Gillespie-chap1"/> The World Trade Center plans involved evicting these business owners, some of whom fiercely protested the forced relocation.<ref name="Gillespie-chap1"/> In June 1962, a group representing approximately 325 shops and 1,000 other affected small businesses filed an [[injunction]], challenging the Port Authority's power of [[eminent domain]].<ref>{{cite news |title=Injunction Asked on Trade Center |date=June 27, 1962 |publisher=The New York Times |author=Clark, Alfred E.}}</ref> The dispute with local business owners worked its way through the court system, up to the [[New York Court of Appeals|New York State Court of Appeals]], which in April 1963 upheld the Port Authority's right of eminent domain, saying that the project had a "public purpose".<ref>{{cite news |title=World Trade Center Here Upheld by Appeals Court |author=Crowell, Paul |publisher=The New York Times |date=April 5, 1963}}</ref><ref>{{cite news |title=Merchants Ask Supreme Court to Bar Big Trade Center Here |publisher=The New York Times / Associated Press |date=August 26, 1963}}</ref> On [[November 12]] [[1963]], the [[Supreme Court of the United States|United States Supreme Court]] refused to accept the case.<ref name="nyt-1963nov13">{{cite news |title=High Court Plea is Lost by Foes of Trade Center |author=Arnold, Martin |publisher=The New York Times |date=November 13, 1963}}</ref><ref>[http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=CASE&court=US&vol=375&page=78 375 US. 4] - ''Courtesy Sandwich Shop, Inc., et al. v. Port of New York Authority''</ref> Under the state law, the Port Authority was required to assist business owners in relocating, though many business owners regarded what the Port Authority offered as inadequate.<ref name="nyt-1963nov13"/><ref>{{cite news |title=Port Body Raises Relocation Aid |author=Apple, Jr. R.W. |publisher=The New York Times |date=November 16, 1963}}</ref> Questions continued while the World Trade Center was constructed, as to whether the Port Authority really ought to take on the project, described by some as a "mistaken social priority".<ref>{{cite news |title=Kheel Urges Port Authority to Sell Trade Center |date=November 12, 1969 |publisher=The New York Times}}</ref>

Private [[real estate]] developers and members of the Real Estate Board of New York also expressed concerns about this much "subsidized" office space going on the open market, competing with the private sector when there was already a glut of vacancies.<ref name="Gillespie-chap1"/><ref>{{cite news |title=New Fight Begun on Trade Center |author=Knowles, Clayton |date=February 14, 1964 |publisher=The New York Times}}</ref> An especially vocal critic was Lawrence A. Wien, owner of the [[Empire State Building]], which would lose its title of [[List of tallest buildings and structures in the world|tallest building in the world]].<ref name="Gillespie-chap1"/><ref>{{cite news |title=Critics Impugned on Trade Center |author=Ennis, Thomas W. |date=February 15, 1964 |publisher=The New York Times}}</ref> Wien organized a group of builders into a group called the "Committee for a Reasonable World Trade Center" which demanded the project be scaled down.<ref>{{cite news |title=All Major Builders are Said to Oppose Trade Center Plan |author=Knowles, Clayton |date=March 9, 1964 |publisher=The New York Times}}</ref>

In January 1964, the Port Authority inked a deal with the State of New York to locate government offices at the World Trade Center.<ref>{{cite news |title=State Will Rent at Trade Center |author=Sibley, John |publisher=The New York Times |date=January 14, 1964}}</ref> The Port Authority began signing up some commercial tenants in the Spring and Summer of 1964, including several banks.<ref>{{cite news |title=4th Bank Signed by Trade Center |date=July 14, 1964 |publisher=The New York Times}}</ref> In 1965, the Port Authority signed up the [[United States Customs Service]] as a tenant.<ref>{{cite news |title=Customs to Move to Trade Center |author=Fowler, Glenn |date=July 7, 1965 |publisher=The New York Times}}</ref>

A final obstacle for the Port Authority was getting approval from New York City Mayor [[John Lindsay]] and the [[New York City Council]]. They raised concerns about the limited extent that the Port Authority involved the city in the negotiations and deliberations. Negotiations between The City of New York and the Port Authority were centered on tax issues. A final agreement was made on [[August 3]] [[1966]], that the Port Authority would make annual payments to the city in lieu of taxes, for the portion of the World Trade Center leased to private tenants.<ref>{{cite news |title=City Ends Fight with Port Body on Trade Center |author=Smith, Terence |date=August 4, 1966 |publisher=The New York Times}}</ref> In subsequent years, the payments would rise as the overall [[Property tax|real estate tax]] rate increased.<ref>{{cite news |title=Mayor Signs Pact on Trade Center |author=Smith, Terence |publisher=The New York Times |date=January 26, 1967}}</ref>

==Design==
On [[September 20]] [[1962]], the Port Authority announced the selection of [[Minoru Yamasaki]] as lead architect, and [[Emery Roth|Emery Roth & Sons]] as associate architects.<ref>{{cite news |title=Architect Named for Trade Center |author=Esterow, Milton |date=September 21, 1962 |publisher=The New York Times}}</ref> Originally, Yamasaki came back to the Port Authority with the concept of twin towers, but with each building only 80 stories tall. Yamasaki remarked that the "obvious alternative, a group of several large buildings, would have looked like a housing project".<ref name="nyt-1964jan19a">{{cite news |title=A New Era Heralded |author=Huxtable, Ada Louise |publisher=The New York Times |date=January 19, 1964}}</ref>
[[Image:World Trade Center Building Design with Floor and Elevator Arrangment.svg|thumb|250px|A typical floor layout and elevator arrangement of the WTC towers]]
To meet the Port Authority's requirement to build 10 million [[Square foot|square feet]] (930,000 m²) of office space, the buildings would each need to be 110 stories tall. A major limiting factor in building heights were elevators. The taller the building, the more [[elevator]]s are needed to service the building, requiring more space-consuming elevator banks.<ref>{{cite news |title=Biggest Buildings Herald New Era |author=Huxtable, Ada Louise |date=January 26, 1964 |publisher=The New York Times}}</ref> Yamasaki and the engineers decided to use a new system with sky lobbies, which are floors where people can switch from a large-capacity express elevator, which goes only to the sky lobbies, to a local elevator that goes to each floor in a section. The local elevators were stacked on top of each other, within the same elevator shaft. Located on the 44th and 78th floors of each tower, the sky lobbies enabled the elevators to be used efficiently, while also increasing the amount of usable space on each floor from 62 to 75 percent by reducing the number of required elevator shafts.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 9 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> The World Trade Center towers were the second [[supertall]] buildings to use sky lobbies, after the [[John Hancock Center]] in [[Chicago]].<ref>{{cite web |url= http://www.otis.com/otis150/section/1,2344,ARC3066_CLI1_RES1_SEC5,00.html|publisher=[[Otis Elevator Company]]|title= Otis History: The World Trade Center|accessdate=2006-12-07}}</ref> This system was inspired by the [[New York City Subway]] system, whose lines include local stations where local trains stop and express stations where all trains stop.<ref name="gillespie-p76">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 76}}</ref>
[[Image:Wtc_model_at_skyscraper_museum.jpg|thumb|left|185px|Original architectural and engineering model]]
Yamasaki's design for the World Trade Center was unveiled to the public on [[January 18]] [[1964]], with an eight-foot model.<ref name="nyt-1964jan19a"/> The towers had a square plan, approximately 207 feet (63 m) in dimension on each side.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 7 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> The buildings were designed with narrow office windows, only 18 [[inch]]es (45 [[Centimetre|cm]]) wide, which reflected on Yamasaki's [[Acrophobia|fear of heights]] and desire to make building occupants feel secure.<ref name="pekala">{{cite news |title=Profile of a lost landmark; World Trade Center |publisher=Journal of Property Management |date=November 1, 2001 |author=Pekala, Nancy}}</ref> Yamasaki's design called for the building facades to be sheathed in aluminum-alloy.<ref name="nyt-1966may29">{{cite news |title=Who's Afraid of the Big Bad Buildings |author=Huxtable, Ada Louise |date=May 29, 1966 |publisher=The New York Times}}</ref> In all, the World Trade Center complex contained six buildings within the 16 acre (6.5 ha) [[City block#Superblock|superblock]].

The World Trade Center design brought criticism of its aesthetics from the [[American Institute of Architects]] and other groups.<ref>{{cite news |title=Marring City's Skyline |author=Steese, Edward |date=March 10, 1964 |publisher=The New York Times}}</ref><ref name="nyt-1966may29"/> [[Lewis Mumford]], author of ''[[The City in History]]'' and other works on [[urban planning]], criticized the project and described it and other new skyscrapers as "just glass-and-metal filing cabinets".<ref>{{cite news |title=Mumford Finds City Strangled By Excess of Cars and People |author=Whitman, Alden |publisher=The New York Times |date=March 22, 1967}}</ref> [[Television]] broadcasters raised concerns that the World Trade Center twin towers would cause interference in television reception for viewers in the [[New York metropolitan area|New York City area]].<ref>{{cite news |title=TV Group Objects to Trade Towers |author=Schumach, Murray |date=February 20, 1966 |publisher=The New York Times}}</ref> In response to these concerns, the Port Authority offered to provide new television transmission facilities at the World Trade Center.<ref>{{cite news |title=TV Mast Offered on Trade Center |date=February 24, 1966 |publisher=The New York Times}}</ref> The [[Linnaean Society]] of the [[American Museum of Natural History]] also opposed the Trade Center project, citing hazards the buildings would impose on [[Bird migration|migrating bird]]s.<ref>{{cite news |title=Big Trade Center Called Bird Trap |author=Knowles, Clayton |publisher=The New York Times |date=March 16, 1967}}</ref>

The structural engineering firm Skilling, Helle, Christiansen, [[Leslie Robertson|Robertson]] worked to implement Yamasaki's design, developing the tube-frame structural system used in the buildings. The Port Authority's Engineering Department served as [[geotechnical engineering|foundation engineers]], Joseph R. Loring & Associates as [[electrical engineering|electrical engineers]], and Jaros, Baum & Bolles as [[mechanical engineering|mechanical engineers]]. [[Tishman Reality & Construction|Tishman Realty & Construction Company]] was the [[general contractor]] on the World Trade Center project. Guy F. Tozzoli, director of the World Trade Department at the Port Authority, and the Port Authority's Chief Engineer, Rino M. Monti, oversaw the project.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF | title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |chapter=Chapter 1 |date=September 2005 |pages=p. 1}}</ref>

===Structural design===
As an interstate agency, the Port Authority was not subject to local laws and regulations of the City of New York, including [[building code]]s. Nonetheless, the Port Authority required architects and structural engineers to follow the New York City building codes. At the time when the World Trade Center was planned, new building codes were being devised to replace the 1938 version that was in place. The structural engineers ended up following draft versions of the new 1968 building codes which incorporated "advanced techniques" in [[building design]].<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xxxviii |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>

The World Trade Center towers included many [[structural engineering]] innovations in [[skyscraper design and construction]], which allowed the buildings to reach new heights and become the [[List of tallest buildings in the world|tallest]] in the world. Traditionally, [[skyscraper]]s used a skeleton of [[column]]s distributed throughout the interior to support building loads, with interior columns disrupting the floor space. The tube-frame concept was a major innovation, allowing open floor plans and more space to rent. The buildings used high-strength, load-bearing perimeter [[steel]] columns called [[Truss#Vierendeel truss|Vierendeel trusses]] that were spaced closely together to form a strong, rigid wall structure. There were 59 perimeter columns, narrowly spaced on each side of the buildings. These were designed to provide support for virtually all lateral loads (such as wind loads) and to share the gravity loads with the core columns.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |format =PDF |date=September 2005 |chapter=Chapter 1 |pages=p. 6}}</ref> Structural analysis of major portions of the World Trade Center were computed on an [[IBM 1620]].<ref>{{cite journal | last = Taylor | first = R. E. | year = 1966 | month = December | title = Computers and the Design of the World Trade Center | journal = [[ASCE]], Structural Division | volume = 92 | issue = ST-6 | pages = pp. 75-91}}</ref>
[[Image:Nistncstar1-1-fig2-4.png|thumb|right|Typical WTC architectural floor plan]]

The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected together by [[wikt:spandrel|spandrel]] plates. The perimeter columns had a square cross section, 14 inches (36 cm) on a side, and were constructed of welded steel plate.<ref name="NIST-chapter1">{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |date=September 2005}}</ref> The thickness of the plates and grade of [[structural steel]] varied over the height of the tower, ranging from 36,000 to 100,000 pounds per square inch<ref>[[A36 steel]] has a nominal [[Yield (engineering)|yield strength]] of 36,000 to 100,000 pounds per square inch.</ref> (260 to 670 MPa). The strength of the steel and thickness of the steel plates decreased with height because they were required to support lesser amounts of building mass on higher floors.<ref name="NIST-chapter1"/> The tube-frame design required 40 percent less structural steel than conventional building designs.<ref name="steel">{{cite journal |author=American Iron and Steel Institute |title=The World Trade Center - New York City |journal=Contemporary Steel Design |volume=1(4) |year=1964 |publisher=American Iron and Steel Institute}}</ref> From floor #7 to the ground level and down to the foundation, the columns were spaced 10 feet (3 m) apart.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |date=September 2005 |pages=p. 10}}</ref> All columns were founded on [[bedrock]], which unlike that in Midtown Manhattan, where the bedrock is shallow, is at 65–85 feet (20–26 m) below the surface.<ref>{{cite journal |url=http://www.nae.edu/nae/bridgecom.nsf/weblinks/CGOZ-58NLJ9?OpenDocument |title=World Trade Center "Bathtub": From Genesis to Armageddon |journal=Bridges |author=Tamaro, George J. |date=Spring 2002 |volume=32(1)}}</ref>

The spandrel plates were welded to the columns to create the modular pieces off-site at the fabrication shop.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |date=September 2005 |pages=p. 8}}</ref> The modular pieces were typically 52 inches (1.3 m) deep, and extended for two full floors and half of two more floors.<ref name="NIST-chapter1"/> Adjacent modules were bolted together, with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, and served to transmit [[shear stress]] between columns, thus allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.<ref name="NIST-chapter1"/>

The building's core housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m), and contained 47 steel columns running from the bedrock to the top of the tower.<ref name="NIST-chapter1"/> The columns tapered with height, and consisted of welded box-sections at lower floors and rolled wide-flange sections at upper floors. The core in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. All of the elevators were located in the core. Each building had three stairwells that were also located in the core, except on the [[mechanical floor]]s where they were located outside of the structural core.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 8 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>
[[Image:Wtc floor truss system.png|thumb|left|Schematic of composite floor truss system]]
The large, column-free space between the perimeter and core was bridged by pre-fabricated floor trusses. The floors supported their own weight, as well as [[live loads]], provided lateral stability to the exterior walls, and distributed wind loads among the exterior walls. The floors consisted of 4 inch (10 cm) thick lightweight [[concrete]] slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet (18.2 m) in the long-span areas and 35 feet (11 m) in the short span area.<ref name="NIST-chapter1"/> The trusses connected to the perimeter at alternate columns, and were therefore on 6 foot 8 inch (2.03 m) centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandrel plates with [[Viscoelasticity|viscoelastic]] dampers, which helped reduce the amount of sway felt by building occupants. The trusses supported a 4 inch thick (10 cm) lightweight concrete floor slab, with shear connections for composite action.<ref name="NIST-chapter1"/>

Hat [[truss]]es (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communications [[Antenna (radio)|antenna]] on top of each building.<ref name="NIST-chapter1"/> Only 1 WTC (north tower) actually had an antenna fitted, which was added in 1978.<ref>{{cite web |url=http://www.pbs.org/wgbh/amex/newyork/sfeature/sf_building.html |title=New York: A Documentary Film - The Center of the World (Construction Footage) |publisher = Port Authority / PBS |accessdate=2007-05-16}}</ref> The truss system consisted of six trusses along the long axis of core and four along the short axis. This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower.

===Wind effects===
The tube frame design using steel core and perimeter columns protected with sprayed-on fire resistant material created a relatively lightweight structure that would sway more in response to the wind, compared to traditional structures such as the [[Empire State Building]] that have thick, heavy [[masonry]] for [[fireproofing]] of steel structural elements.<ref>{{cite book |title=City in the Sky |author=Glanz, James and Eric Lipton |pages=p. 138 |publisher=Times Books |year=2003}}</ref> During the design process, [[wind tunnel]] tests were done at [[Colorado State University]] and at the [[National Physical Laboratory, UK|National Physical Laboratory]] in the [[United Kingdom|U.K.]] to establish design wind pressures that the World Trade Center towers could be subjected to and structural response to those forces.<ref>{{cite book |title=Design and Construction of Structural Systems (NCSTAR 1-1A) |publisher=National Institute of Standards and Technology |pages=p. 65 |author=Fanella, David A., Arnaldo T. Derecho, S.K. Ghosh |date=September 2005}}</ref> Experiments were also done to evaluate how much sway occupants could tolerate. Subjects were recruited for "free eye exams", while the real purpose of the experiment was to subject them to simulated building sway and find out how much they could comfortably tolerate.<ref>{{cite book |title=City in the Sky |author=Glanz, James and Eric Lipton |pages=p. 139-144 |publisher=Times Books |year=2003}}</ref> Many subjects did not respond well, experiencing [[dizziness]] and other ill effects. The chief engineer [[Leslie Robertson]] worked with Canadian engineer Alan G. Davenport to develop viscoelastic [[Damping|dampers]] to absorb some of the sway. These viscoelastic dampers, used throughout the structures at the joints between floor trusses and perimeter columns, along with some other structural modifications reduced the building sway to an acceptable level.<ref>{{cite book |title=City in the Sky |author=Glanz, James and Eric Lipton |pages=p. 160-167 |publisher=Times Books |year=2003}}</ref>

===Fire protection===
[[Fireproofing|Sprayed-fire resistant material]]s (SFRMs) were used to protect some structural steel elements in the towers, including all floor trusses and beams.<ref name="NCSTAR 1-1-p8">{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 8 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> [[Gypsum]] [[wallboard]] in combination with SFRMs, or in some cases gypsum wallboard alone, was used to protect core columns.<ref name="NCSTAR 1-1-p8"/> [[Vermiculite]] plaster was used on the interior-side and SFRMs on the other three sides of the perimeter columns for fire protection.<ref name="NCSTAR 1-1-p8"/> The 1968 New York City building codes were more lenient in some aspects of fire protection, such as allowing three exit stairwells in the World Trade Center towers, instead of six as required under older building codes.<ref name="NCSTAR 1-1-p153">{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 153 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>

The 1968 New York City building codes did not require [[Fire sprinkler|sprinkler]]s for [[high-rise]] buildings, except for underground spaces. In accordance with building codes, sprinklers were originally installed only in the underground parking structures of the World Trade Center.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 162 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> Following a major fire in February 1975, the Port Authority decided to start installing sprinklers throughout the buildings. By 1993, nearly all of Tower 2 [South Tower] and 85% of Tower 1 had sprinklers installed,<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 163 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> and the entire complex was retrofitted by 2001.<ref>{{cite book |title=Active Fire Protection Systems (NCSTAR 1-4) |publisher=National Institute of Standards and Technology |pages=p. 14 |author=Evans, David D., Richard D. Peacock, Erica D. Kuligowski, W. Stuart Dols, William L. Grosshandler |date=September 2005}}</ref>

==Construction==
In March 1965, the Port Authority began acquiring property at the World Trade Center site.<ref>{{cite news |title=Port Agency Buys Downtown Tract |author=Ingraham, Joseph C. |date=March 29, 1965 |publisher=The New York Times}}</ref> The Ajax Wrecking and Lumber Corporation was hired for the [[demolition]] work, which began on [[March 21]] [[1966]] to clear the site for construction of the World Trade Center.<ref name="gillespie-p61">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 61}}</ref>

[[Groundbreaking]] was on [[August 5]] [[1966]], marking the beginning of construction of the World Trade Center's foundations.<ref>{{cite news |title=Jackhammers Bite Pavement to Start Trade Center Job |date=August 6, 1966 |publisher=The New York Times}}</ref> The site of the World Trade Center was located on [[landfill]], with the bedrock located 65 feet (20 m) below.<ref name="iglauer">{{cite news |title=The Biggest Foundation |author=Iglauer, Edith |date=November 4 1972 |publisher=The New Yorker}}</ref> In order to construct the World Trade Center, it was necessary to build the "bathtub", with the [[slurry wall]] along the [[West Side Highway|West Street]] side of the site, to keep water from the [[Hudson River]] out. This method was used in place of conventional dewatering methods because lowering the [[groundwater table]] would cause large [[settlement (construction)|settlements]] of nearby buildings not built on [[deep foundation]]s.<ref>{{cite news |title=Tall Towers will Sit on Deep Foundations |last=Kapp |first=Martin S |publisher=Engineering News Record |date=July 9, 1964}}</ref> The slurry method involves digging a [[trench]], and as [[excavation]] proceeds, filling the space with a "slurry" mixture, composed of [[bentonite]] which plugs holes and keeps water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out. The "slurry" method was devised by Port Authority chief engineer John M. Kyle, Jr. Towards the end of 1966, work began on building the slurry wall, led by [[Montreal]]-based Icanda, a subsidiary of an Italian engineering firm, Impresa Costruzioni Opere Specializzate (I.C.O.S.).<ref name="gillespie-p68">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 68}}</ref> It took fourteen months for the slurry wall to be completed, which was necessary before excavation of material from the interior of the site could begin.<ref name="gillespie-p68"/> The original [[Downtown Hudson Tubes|Hudson Tubes]], which carried PATH trains into Hudson Terminal, remained in service as elevated tunnels until 1971 when a new [[World Trade Center (PATH station)|PATH station]] was built.<ref>{{cite news |author=Carroll, Maurice |title=A Section of the Hudson Tubes is Turned into Elevated Tunnel |date=December 30, 1968 |publisher=The New York Times}}</ref>
[[Image:Wtc panynj 1973.jpg|thumb|right|200px|World Trade Center in 1973]]
[[Construction|Construction work]] began on the North Tower in August 1968 with construction beginning on the South Tower by January 1969.<ref name="pbstimeline">{{cite web |url=http://www.pbs.org/wgbh/amex/newyork/timeline/index.html |title=Timeline: World Trade Center chronology |publisher=PBS - American Experience |accessdate=2007-05-15}}</ref> In January 1967, $74 million in contracts were awarded to the [[PACCAR|Pacific Car and Foundry Company]], [[Laclede Steel Company]], [[U.S. Steel|Granite City Steel Company]], and [[Karl Koch Steel Consulting|Karl Koch Erecting Company]] to supply [[steel]] for the project.<ref name="nyt-1967jan24">{{cite news |title=Contracts Totaling $74,079,000 Awarded for the Trade Center |publisher=The New York Times |date=January 24, 1967}}</ref> The Port Authority chose to use many different steel suppliers, bidding on smaller portions of steel, rather than buy larger amounts from a single source such as [[Bethlehem Steel]] or [[U.S. Steel]] as a cost-saving measure.<ref name="gillespie-p83">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 83}}</ref> Karl Koch was also hired to do all the work of erecting the steel, and a contract for work on the aluminum facade was awarded to the [[Alcoa|Aluminum Company of America]].<ref name="nyt-1967jan24"/> [[Tishman Realty & Construction]] was hired in February 1967 to oversee construction of the project.<ref>{{cite news |title=Trade Center Job To Go To Tishman |author=Kihss, Peter |publisher=The New York Times |date=February 27, 1967}}</ref>

Extensive use of [[prefabrication|prefabricated]] parts for the perimeter framing and floor truss systems helped speed up the construction process and reduce costs, while providing greater [[quality control]].<ref name="steel"/> Steel components were freighted into a [[Penn Central Transportation|Penn Central]] yard in [[Jersey City, New Jersey|Jersey City]]. From there, they were brought in early morning hours through the [[Holland Tunnel]] to the construction site, and lifted into place by a [[Crane (machine)|crane]].<ref>{{cite news |title=Trade Center is Doing Everything Big |publisher=The New York Times |date=June 6, 1969 |author=Kaufman, Micheal T.}}</ref> Larger pieces were brought to the construction site by [[tugboat]]s.<ref name="gillespie-p88">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 88}}</ref> A special type of crane, suitable for constructing such tall buildings, that used [[hydraulics]] to lift components and provided its own power was used in construction of the World Trade Center. The Favco Standard 2700 Crane, manufactured by Favelle Mort Ltd. of [[New South Wales]], [[Australia]] was informally called a "[[kangaroo]] crane".<ref name="gillespie-p92">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 92-94}}</ref>

In 1970, tugboat workers went on [[Strike action|strike]], halting the transport of material to the construction site.<ref>{{cite news |title=300 Tugboats Idle as Men Walk Out for Doubled Wage |author=McFadden, Robert D. |date=February 2, 1970 |publisher=The New York Times}}</ref> The Port Authority attempted other means of transporting material, including via [[helicopter]]. When this method was tried, the helicopter lost its load of steel into the [[Kill Van Kull]].<ref name="gillespie-p91">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 91}}</ref> Some other mishaps occurred during the construction process, including disruption of [[telephone]] service in Lower Manhattan when telephone cables were crushed by [[pile driver]]s.<ref>{{cite news |author=Carroll, Maurice |title=Phones Disrupted by a Pile Driver |date=March 19, 1969 |publisher=The New York Times}}</ref> On [[March 16]] [[1970]], a [[propane]] gas explosion injured six workers when a truck hit a propane tank.<ref>{{cite news |title=Propane Blast Hits Trade Center |author=Van Gelder, Lawrence |date=March 17, 1970 |publisher=The New York Times}}</ref> In all, 60 workers were killed in construction accidents while the World Trade Center was being built.<ref>{{cite web |url=http://www.pbs.org/americarebuilds/engineering/engineering_qfacts.html |title=America Rebuilds: Quick Facts |publisher=PBS |accessdate=2007-05-15}}</ref>

Construction of 1 World Trade Center (North Tower) was completed on [[December 23]] [[1970]], with 2 World Trade Center (South Tower) completed on [[July 19]] [[1971]].<ref name="pbstimeline"/> The first tenants moved into the North Tower in December 1970, and into the South Tower in January 1972.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xxxvi |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> The buildings were dedicated on [[April 4]] [[1973]]; Tobin, who had resigned the year before, was absent from the ceremonies.<ref name="Darton-chap6">Darton, Eric (1999) ''Divided We Stand: A Biography of New York's World Trade Center'', Chapter 6, Basic Books.</ref>

Building the World Trade Center involved excavating 1.2 million [[cubic yard]]s (917,000 [[Cubic metre|m³]]) of material.<ref name="gillespie-p71">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 71}}</ref> Rather than transporting this material at great costs out to sea or to landfills in [[New Jersey]], the fill material was used to expand the [[Manhattan]] shoreline across West Street.<ref name="gillespie-p71"/> Work to demolish the [[pier]]s began on [[January 5]] [[1967]], including Pier 7 to Pier 11 which were all constructed around 1910.<ref>{{cite news |title=Demolition Begun on 5 City Piers |author=Horne, George |publisher=The New York Times |date=January 5, 1967}}</ref> The demolition work moved forward, despite conflicts between [[David Rockefeller]], Governor [[Nelson Rockefeller]] and Mayor [[John Lindsay]] regarding plans for [[Battery Park City, Manhattan|Battery Park City]].<ref>{{cite news |title=Conflicts Stall Landfill Plans |author=Roberts, Steven V. |publisher=The New York Times |date=January 17, 1967}}</ref> Landfill material from the [[World Trade Center]] was used to add land, and a cellular [[cofferdam]] was constructed to retain the material.<ref name="iglauer">{{cite news |url=http://www.newyorker.com/archive/content/articles/010924fr_archive02 |title=The Biggest Foundation |author=Iglauer, Edith |date=November 4 1972 |publisher=The New Yorker}}</ref> The result was a 700 foot (210 m) extension into the Hudson River, running six blocks or 1,484 feet (450 m).<ref name="gillespie-p71"/> This land was a "gift" to New York City, allowing more [[tax]]-generating developments in Battery Park City.<ref>{{cite news |title=New York Gets $90 Million Worth of Land for Nothing |publisher=Engineering News Record |date=April 18, 1968}}</ref>

The original estimates put forth by the Port Authority had the costs for construction of the World Trade Center at $350 million — an optimistic figure.<ref name="gillespie-p70">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 70}}</ref> In December 1966, the Port Authority announced increased cost estimates, bringing the estimated total to $575 million.<ref name="gillespie-p69">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 69}}</ref> This announcement brought criticism of the project from private real estate developers, ''[[The New York Times]]'', and others in New York City.<ref>{{cite news |title=Questions on the Trade Center |publisher=The New York Times |date=December 24, 1966}}</ref> The critics charged that the Port Authority figure was an unrealistically low estimate, and they estimated the project would end up costing $750 million.<ref>{{cite news |title=Estimate Raised for Trade Center |author=Phillips, McCandlish |date=December 29, 1966 |publisher=The New York Times}}</ref> When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.<ref name="Cudahy">Cudahy, Brian J. (2002) ''Rails Under the Mighty Hudson: The Story of the Hudson Tubes, the Pennsy Tunnels, and Manhattan Transfer'', Chapter 3, Fordham University Press.</ref> The project was financed through [[Tax exemption|tax-exempt]] [[Bond (finance)|bond]]s issued by the Port Authority.<ref>{{cite news |author=Allan, John H. |title=Bonds: Port of New York Authority to Raise $100-Million |date=February 28, 1968 |publisher=The New York Times}}</ref>

==Other buildings==
The World Trade Center complex included four other smaller buildings constructed during the 1970s. 3 World Trade Center was a 22-story building, which was home to the [[Marriott World Trade Center]]. It was designed by [[Skidmore, Owings and Merrill]] in 1978-79.<ref>{{cite book |author=McAllister, Therese, Johnathan Barnett, John Gross, Ronald Hamburger, Jon Magnusson |chapter=WTC3 |title=World Trade Center Building Performance Study |publisher=FEMA |date=May 2002}}</ref> [[4 World Trade Center]], [[5 World Trade Center]], and [[6 World Trade Center]] were all 8-9 story buildings that were designed by the same team as the Twin Towers, including Minoru Yamasaki, Emery Roth & Sons, and Skilling, Helle, Christiansen, Robertson.<ref>{{cite book |author=McAllister, Therese, Johnathan Barnett, John Gross, Ronald Hamburger, Jon Magnusson |chapter=WTC4, 5, and 6 |title=World Trade Center Building Performance Study |publisher=FEMA |date=May 2002}}</ref> A seventh building ([[7 World Trade Center]]) was built in the mid-1980s, just to the north of the main World Trade Center site. The 47-story building was designed by Emery, Roth & Sons, and constructed on top of a [[Con Edison]] power [[substation]].<ref>{{cite book |author=McAllister, Therese, Johnathan Barnett, John Gross, Ronald Hamburger, Jon Magnusson |chapter=WTC7 |title=World Trade Center Building Performance Study |publisher=FEMA |date=May 2002}}</ref>

==Modifications==
Over time, numerous structural modifications were made to suit the needs of tenants in the Twin Towers. Modifications were made in accordance with the Port Authority's ''Tenant Alteration Review Manual'' and were reviewed by the Port Authority to ensure the changes did not compromise structural integrity of the buildings. Oftentimes, openings were cut in the floors to allow new stairways to be built to connect tenant floors. Some steel beams in the core were reinforced and strengthened to accommodate heavy live loads, such as large amounts of heavy files that tenants had on their floors.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xliv |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>

Repairs to structural elements on the lower levels of 1 WTC [North Tower] were made following the [[1993 World Trade Center bombing]]. The greatest damage occurred on levels B1 and B2, with significant structural damage also on level B3.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xlv |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> Primary structural columns were not damaged, but secondary steel members experienced some damage.<ref>{{cite web |url=http://www.interfire.org/res_file/pdf/Tr-076.pdf |format =PDF |title=Experiences of the Chief Engineer of the Port Authority |author=Fasullo, Eugene |publisher=United States Fire Administration |accessdate=2007-05-15}}</ref> Floors that were blown out needed to be repaired, to restore the structural support they provided to columns.<ref>{{cite web |url=http://www.interfire.org/res_file/pdf/Tr-076.pdf |format =PDF |title=The World Trade Center Complex |author=Port Authority Risk Management Staff |publisher=United States Fire Administration |accessdate=2007-05-15}}</ref> The slurry wall was in peril following the bombing and loss of the floor slabs which provided lateral support to counteract pressure from Hudson River water on the other side.<ref name="ennala">{{cite journal |author=Ramabhushanam, Ennala and Marjorie Lynch |title=Structural Assessment of Bomb Damage for World Trade Center |journal=Journal of Performance of Constructed Facilities |volume=8(4) |pages=229-242}}</ref> The [[refrigeration]] plant on sublevel B5, which provided [[air conditioning]] to the entire World Trade Center complex, was heavily damaged and replaced with a temporary system for the summer of 1993.<ref name="ennala"/> The [[fire alarm]] system for both towers needed to be replaced, after critical wiring and signaling in the original system was destroyed in the 1993 bombing. Installation of the new system took years to complete, and replacement of some components was still underway at the time of the [[September 11, 2001 attacks]].<ref>{{cite book |title=Active Fire Protection Systems (NCSTAR 1-4) |publisher=National Institute of Standards and Technology |pages=p. 44 |author=Evans, David D., Richard D. Peacock, Erica D. Kuligowski, W. Stuart Dols, William L. Grosshandler |date=September 2005}}</ref>

==See also==
*[[Collapse of the World Trade Center]]
*[[Freedom Tower]]
*[[150 Greenwich Street]]
*[[175 Greenwich Street]]
*[[200 Greenwich Street]]
*[[Plans to rebuild the World Trade Center]]
*[[Philippe Petit]], who wirewalked between the two towers

==References==
{{reflist|2}}

==External links==
*[http://www.pbs.org/wgbh/amex/newyork/sfeature/sf_building.html New York: A Documentary Film - The Center of the World] - ''Building the World Trade Center'', an 18-minute film, with construction footage, produced by the Port Authority in 1983
*[http://www.skyscraper.org/WHAT%27S_UP/WTC_DOSSIER/wtc.htm World Trade Center] - Skyscraper Museum
*{{Cite web
| title = Corus in construction - Systems evolution
| accessdate = 2007-05-14
| url = http://corusconstruction.com/en/reference/teaching_resources/architectural_studio_reference/design/tall_building_designs/systems_evolution/
}}
*[http://wtc.nist.gov/ NIST and the World Trade Center]
*[http://www.ericdarton.net/ New York's World Trade Center - A Living Archive] - by author, Eric Darton
*[http://www.antiqueradio.com/Sep02_RadioRow_Steinhardt.html The Death of New York's Radio Row], by Syd Steinhard - Downtown Express

{{WTC navigation}}
{{Featured article}}

[[Category:World Trade Center]]
[[Category:Building projects|World Trade Center]]

Bau des World Trade Centers

2007-07-11T18:37:44Z

RTC: /* Structural design */

{{for|the post-9/11 rebuilding and ongoing construction at the World Trade Center site|World Trade Center site}}
[[Image:World trade center new york city construction flickr.png|thumb|right|250px|View of the World Trade Center's construction from across the [[Hudson River]]]]
The '''building of the [[World Trade Center]]''' started as a post-[[World War II]] [[urban renewal]] project, spearheaded by [[David Rockefeller]], to help revitalize [[Lower Manhattan]]. The project was developed by the [[Port Authority of New York and New Jersey]], which hired architect [[Minoru Yamasaki]] who came up with the specific idea for twin towers. After extensive negotiations, the [[New Jersey]] and [[New York|New York State]] governments, which oversee the Port Authority, agreed to support the World Trade Center project at the [[Radio Row]] site on the lower-west side of [[Manhattan]]. To make the agreement acceptable to New Jersey, the Port Authority agreed to take over the bankrupt Hudson & Manhattan Railroad (renamed as [[Port Authority Trans-Hudson|PATH]]), which brought commuters from New Jersey to the Lower Manhattan site.

The towers were designed as framed tube structures, which provided tenants with open floor plans, uninterrupted by columns or walls. This was accomplished using numerous, closely-spaced perimeter columns to provide much of the strength to the structure, along with gravity load shared with the core columns. The [[elevator]] system, which made use of [[sky lobby|sky lobbies]] and a system of express and local elevators, allowed substantial floor space to be freed up for use as office space by making the structural core smaller. The design and construction of the World Trade Center twin towers involved many other innovative techniques, such as the [[slurry wall]] for digging the [[Foundation (architecture)|foundation]], and [[wind tunnel]] experiments. Construction of the World Trade Center's North Tower began in August 1968, and the South Tower in 1969. Extensive use of prefabricated components helped to speed up the construction process. The first tenants moved into the North Tower in December 1970 and into the South Tower in January 1972. Four other, low-level buildings were constructed as part of the World Trade Center in the 1970s, and a [[7 World Trade Center|seventh]] building was constructed in the mid-1980s.

==Planning==
In 1942, [[Austin J. Tobin]] became the Executive Director of the [[Port Authority of New York and New Jersey|Port Authority]], beginning a 30-year career during which he oversaw the planning and development of the World Trade Center.<ref name="Doig-chap1">{{cite book |last=Doig |first=Jameson W. |title=Empire on the Hudson |year=2001 |publisher=Columbia University Press |chapter=Chapter 1}}</ref> The concept of establishing a "[[World Trade Center (disambiguation)|world trade center]]" was conceived during the post-[[World War II]] period, when the [[United States]] thrived economically and international trade was increasing. In 1946, the [[New York State Legislature]] passed a bill that called for a "world trade center" to be established.<ref name="nyt-07061946">{{cite news |title=Dewey Picks Board for Trade Center |publisher=The New York Times |date=July 6, 1946}}</ref> The World Trade Corporation was set up and a board appointed by New York Governor [[Thomas E. Dewey]] to develop plans for the project.<ref name="nyt-07061946"/> Architect [[John Eberson]] and his son Drew devised a plan that included 21 buildings over a ten-block area, at an estimated cost of $150 million.<ref>{{cite news |title=Plans are Tabled for Trade Center |author=Crisman, Charles B. |publisher=The New York Times |date=November 10, 1946}}</ref> In 1949, the World Trade Corporation was dissolved by the New York State Legislature, and plans for a "world trade center" were put on hold.<ref>{{cite news |title=Lets Port Group Disband, State Senate for Dissolution of World Trade Corporation |publisher=The New York Times |date=March 11, 1949}}</ref>
===Original plans===
[[Image:East-side-wtc.png|thumb|right|300px|Architect's model for the proposed World Trade Center on the East River]]
During the post-war period, economic growth was concentrated in [[Midtown Manhattan]], in part stimulated by the [[Rockefeller Center]], which was developed in the 1930s. Meanwhile, Lower Manhattan was left out of the [[Boom and bust|economic boom]]. One exception was the construction of [[One Chase Manhattan Plaza]] in the [[Financial District, Manhattan|Financial District]], by [[David Rockefeller]], who led [[urban renewal]] efforts in Lower Manhattan.<ref name="Gillespie-chap1">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |chapter=Chapter 1 |publisher=Rutgers University Press}}</ref> In 1958, Rockefeller established the Downtown-Lower Manhattan Association (DLMA), which commissioned [[Skidmore, Owings and Merrill]] to draw up plans for revitalizing [[Lower Manhattan]]. The plans, made public in 1960, called for a World Trade Center to be built on a 13 [[acre]] (5.25 [[Hectare|ha]]) site along the [[East River]], from [[Old Slip]] to [[Fulton Street (Manhattan)|Fulton Street]] and between [[Water Street (Manhattan)|Water Street]] and [[South Street (Manhattan)|South Street]].<ref name="Levinson">{{cite book|last=Levinson |first=Leonard Louis| title=Wall Street| year=1961| publisher=Ziff Davis Publishing| location=New York| page=346}}</ref><ref name="nyt-01271960">{{cite news |title=A World Center of Trade Mapped Off Wall Street |date=January 27, 1960 |publisher=The New York Times |author=Grutzner, Charles}}</ref> The complex would include a 900 [[Foot (unit of length)|foot]] (275 [[Metre|m]]) long [[Convention center|exhibition hall]], and a 50-70 story building, with some of its upper floors used as a hotel.<ref>{{cite book |title=Men of Steel: The Story of the Family That Built the World Trade Center |author=Koch, Karl III |publisher=Three Rivers Press |year=2002 |pages=p. 173}}</ref> Other amenities would include a theater, shops, and restaurants.<ref name="dlma-plan">{{cite news |title=Text of Trade Center Report by the Downtown-Lower Manhattan Association |publisher= The New York Times |date=January 27, 1960}}</ref> The plan also called for a new [[securities]] exchange building, which the Downtown-Lower Manhattan Association hoped would house the [[New York Stock Exchange]].<ref name="nyt-01271960"/>

David Rockefeller suggested that the Port Authority would be a logical choice for taking on the project.<ref name="nyt-01271960"/> Rockefeller argued that the Trade Center would provide great benefits in facilitating and increasing volume of international commerce coming through the Port of New York.<ref name="dlma-plan"/> Given the importance of [[New York City]] in global commerce, Port Authority director Austin J. Tobin remarked that the proposed project should be ''the'' World Trade Center, and not just ''a'' "world trade center".<ref>{{cite news |title=Tobin Says Proposed Center Should Be World's Best |publisher=The New York Times |date=May 5, 1960}}</ref> After a year-long review of the proposal, the Port Authority formally backed the project on [[March 11]], [[1961]].<ref>{{cite news |title=355 Million World Trade Center Backed by Port Authority Study |publisher=The New York Times |date=March 12, 1961}}</ref>

===Agreement===
[[Image:Wtc locator map.png|thumb|right|300px|Location of World Trade Center and originally proposed site]]
The States of New York and New Jersey also needed to approve the project, given their control and oversight role of the Port Authority. Objections to the plan came from [[New Jersey]] Governor [[Robert B. Meyner]], who resented that [[New York]] would be getting this $335 million project.<ref name="Gillespie-chap1"/> Meanwhile, ridership on New Jersey's [[Hudson and Manhattan Railroad]] (H&M) had declined substantially from a high of 113 million riders in 1927 to 26 million in 1958, after new automobile tunnels and bridges opened across the [[Hudson River]].<ref>{{cite book |title=Rails Under the Mighty Hudson |author=Cudahy, Brian J. |publisher=Fordham University Press |year=2002 |pages=p. 56}}</ref> Towards the end of 1961, negotiations with outgoing New Jersey Governor Meyner regarding the World Trade Center project reached a stalemate. In December 1961, Tobin met with newly elected New Jersey Governor [[Richard J. Hughes]], and made a proposal to shift the World Trade Center project to a west side site where the [[Hudson Terminal]] was located.<ref name="nyt-1961dec29">{{cite news |title=Port Unit Backs Linking of H&M and Other Lines |author=Grutzner, Charles |publisher=The New York Times |date=December 29, 1961}}</ref> In acquiring the Hudson & Manhattan Railroad, the Port Authority would also acquire the Hudson Terminal and other buildings which were deemed obsolete.<ref name="nyt-1961dec29"/> On [[January 22]], [[1962]], the two states reached an agreement to allow the Port Authority to take over the railroad and to build the World Trade Center on Manhattan's lower west side.<ref>{{cite news |title=2 States Agree on Hudson Tubes and Trade Center |author=Wright, George Cable |date=January 23, 1962 |publisher=The New York Times}}</ref> The shift in location for the World Trade Center to a site more convenient to New Jersey, together with Port Authority acquisition of the H&M Railroad, brought New Jersey to agreement in support of the World Trade Center project.

===Controversy===
Even once the agreement between the states of New Jersey, New York, and the Port Authority was finalized, the World Trade Center plan faced continued controversy. The site for the World Trade Center was the location of [[Radio Row]], which was home to hundreds of commercial and industrial tenants, property owners, small businesses, and approximately 100 residents.<ref name="Gillespie-chap1"/> The World Trade Center plans involved evicting these business owners, some of whom fiercely protested the forced relocation.<ref name="Gillespie-chap1"/> In June 1962, a group representing approximately 325 shops and 1,000 other affected small businesses filed an [[injunction]], challenging the Port Authority's power of [[eminent domain]].<ref>{{cite news |title=Injunction Asked on Trade Center |date=June 27, 1962 |publisher=The New York Times |author=Clark, Alfred E.}}</ref> The dispute with local business owners worked its way through the court system, up to the [[New York Court of Appeals|New York State Court of Appeals]], which in April 1963 upheld the Port Authority's right of eminent domain, saying that the project had a "public purpose".<ref>{{cite news |title=World Trade Center Here Upheld by Appeals Court |author=Crowell, Paul |publisher=The New York Times |date=April 5, 1963}}</ref><ref>{{cite news |title=Merchants Ask Supreme Court to Bar Big Trade Center Here |publisher=The New York Times / Associated Press |date=August 26, 1963}}</ref> On [[November 12]], [[1963]], the [[United States Supreme Court]] refused to accept the case.<ref name="nyt-1963nov13">{{cite news |title=High Court Plea is Lost by Foes of Trade Center |author=Arnold, Martin |publisher=The New York Times |date=November 13, 1963}}</ref><ref>[http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=CASE&court=US&vol=375&page=78 375 US. 4] - ''Courtesy Sandwich Shop, Inc., et al. v. Port of New York Authority''</ref> Under the state law, the Port Authority was required to assist business owners in relocating, though many business owners regarded what the Port Authority offered as inadequate.<ref name="nyt-1963nov13"/><ref>{{cite news |title=Port Body Raises Relocation Aid |author=Apple, Jr. R.W. |publisher=The New York Times |date=November 16, 1963}}</ref> Questions continued while the World Trade Center was constructed, as to whether the Port Authority really ought to take on the project, described by some as a "mistaken social priority".<ref>{{cite news |title=Kheel Urges Port Authority to Sell Trade Center |date=November 12, 1969 |publisher=The New York Times}}</ref>

Private [[real estate]] developers and members of the Real Estate Board of New York also expressed concerns about this much "subsidized" office space going on the open market, competing with the private sector when there was already a glut of vacancies.<ref name="Gillespie-chap1"/><ref>{{cite news |title=New Fight Begun on Trade Center |author=Knowles, Clayton |date=February 14, 1964 |publisher=The New York Times}}</ref> An especially vocal critic was Lawrence A. Wien, owner of the [[Empire State Building]], which would lose its title of [[List of tallest buildings and structures in the world|tallest building in the world]].<ref name="Gillespie-chap1"/><ref>{{cite news |title=Critics Impugned on Trade Center |author=Ennis, Thomas W. |date=February 15, 1964 |publisher=The New York Times}}</ref> Wien organized a group of builders into a group called the "Committee for a Reasonable World Trade Center" which demanded the project be scaled down.<ref>{{cite news |title=All Major Builders are Said to Oppose Trade Center Plan |author=Knowles, Clayton |date=March 9, 1964 |publisher=The New York Times}}</ref>

In January 1964, the Port Authority inked a deal with the State of New York to locate government offices at the World Trade Center.<ref>{{cite news |title=State Will Rent at Trade Center |author=Sibley, John |publisher=The New York Times |date=January 14, 1964}}</ref> The Port Authority began signing up some commercial tenants in the Spring and Summer of 1964, including several banks.<ref>{{cite news |title=4th Bank Signed by Trade Center |date=July 14, 1964 |publisher=The New York Times}}</ref> In 1965, the Port Authority signed up the [[United States Customs Service]] as a tenant.<ref>{{cite news |title=Customs to Move to Trade Center |author=Fowler, Glenn |date=July 7, 1965 |publisher=The New York Times}}</ref>

A final obstacle for the Port Authority was getting approval from New York City Mayor [[John Lindsay]] and the [[New York City Council]]. They raised concerns about the limited extent that the Port Authority involved the city in the negotiations and deliberations. Negotiations between The City of New York and the Port Authority were centered on tax issues. A final agreement was made on [[August 3]], [[1966]], that the Port Authority would make annual payments to the city in lieu of taxes, for the portion of the World Trade Center leased to private tenants.<ref>{{cite news |title=City Ends Fight with Port Body on Trade Center |author=Smith, Terence |date=August 4, 1966 |publisher=The New York Times}}</ref> In subsequent years, the payments would rise as the overall [[Property tax|real estate tax]] rate increased.<ref>{{cite news |title=Mayor Signs Pact on Trade Center |author=Smith, Terence |publisher=The New York Times |date=January 26, 1967}}</ref>

==Design==
On [[September 20]], [[1962]], the Port Authority announced the selection of [[Minoru Yamasaki]] as lead architect, and [[Emery Roth|Emery Roth & Sons]] as associate architects.<ref>{{cite news |title=Architect Named for Trade Center |author=Esterow, Milton |date=September 21, 1962 |publisher=The New York Times}}</ref> Originally, Yamasaki came back to the Port Authority with the concept of twin towers, but with each building only 80 stories tall. Yamasaki remarked that the "obvious alternative, a group of several large buildings, would have looked like a housing project".<ref name="nyt-1964jan19a">{{cite news |title=A New Era Heralded |author=Huxtable, Ada Louise |publisher=The New York Times |date=January 19, 1964}}</ref>
[[Image:World Trade Center Building Design with Floor and Elevator Arrangment.svg|thumb|250px|A typical floor layout and elevator arrangement of the WTC towers.]]
To meet the Port Authority's requirement to build 10 million [[Square foot|square feet]] (930,000 m²) of office space, the buildings would each need to be 110 stories tall. A major limiting factor in building heights were elevators. The taller the building, the more [[elevator]]s are needed to service the building and more space-consuming elevator banks.<ref>{{cite news |title=Biggest Buildings Herald New Era |author=Huxtable, Ada Louise |date=January 26, 1964 |publisher=The New York Times}}</ref> Yamasaki and the engineers decided to use a new system with sky lobbies, which are floors where people can switch from a large capacity, express [[elevator]] that goes only to the sky lobbies to a local elevator that goes to each floor in a section. The local elevators were stacked on top of each other, within the same elevator shaft. Located on the 44th and 78th floors of each tower, the sky lobbies enabled the elevators to be used efficiently, while also increasing the amount of usable space on each floor from 62 to 75 percent by reducing the number of required elevator shafts.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 9 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> The World Trade Center towers were the second [[supertall]] buildings to use sky lobbies, after the [[John Hancock Center]] in [[Chicago]].<ref>{{cite web |url= http://www.otis.com/otis150/section/1,2344,ARC3066_CLI1_RES1_SEC5,00.html|publisher=[[Otis Elevator Company]]|title= Otis History: The World Trade Center|accessdate=2006-12-07}}</ref> This system was inspired by the [[New York City Subway]] system, whose lines include local stations where local trains stop and express stations where all trains stop.<ref name="gillespie-p76">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 76}}</ref>
[[Image:Wtc_model_at_skyscraper_museum.jpg|thumb|left|185px|Original architectural and engineering model]]
Yamasaki's design for the World Trade Center was unveiled to the public on [[January 18]], [[1964]], with an eight-foot model.<ref name="nyt-1964jan19a"/> The towers had a square plan, approximately 207 feet (63 m) in dimension on each side.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 7 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> The buildings were designed with narrow office windows, only 18 [[inch]]es (45 [[Centimetre|cm]]) wide, which reflected on Yamasaki's [[Acrophobia|fear of heights]] and desire to make building occupants feel secure.<ref name="pekala">{{cite news |title=Profile of a lost landmark; World Trade Center |publisher=Journal of Property Management |date=November 1, 2001 |author=Pekala, Nancy}}</ref> Yamasaki's design called for the building facades to be sheathed in aluminum-alloy.<ref name="nyt-1966may29">{{cite news |title=Who's Afraid of the Big Bad Buildings |author=Huxtable, Ada Louise |date=May 29, 1966 |publisher=The New York Times}}</ref> In all, the World Trade Center complex contained six buildings within the 16 acre (6.5 ha) [[City_block#Superblock|superblock]].

The World Trade Center design brought criticism of its aesthetics from the [[American Institute of Architects]] and other groups.<ref>{{cite news |title=Marring City's Skyline |author=Steese, Edward |date=March 10, 1964 |publisher=The New York Times}}</ref><ref name="nyt-1966may29"/> [[Lewis Mumford]], author of ''[[The City in History]]'' and other works on [[urban planning]], criticized the project and described it and other new skyscrapers as "just glass-and-metal filing cabinets".<ref>{{cite news |title=Mumford Finds City Strangled By Excess of Cars and People |author=Whitman, Alden |publisher=The New York Times |date=March 22, 1967}}</ref> [[Television]] broadcasters raised concerns that the World Trade Center twin towers would cause interference in television reception for viewers in the [[New York metropolitan area|New York City area]].<ref>{{cite news |title=TV Group Objects to Trade Towers |author=Schumach, Murray |date=February 20, 1966 |publisher=The New York Times}}</ref> In response to these concerns, the Port Authority offered to provide new television transmission facilities at the World Trade Center.<ref>{{cite news |title=TV Mast Offered on Trade Center |date=February 24, 1966 |publisher=The New York Times}}</ref> The [[Linnaean Society]] of the [[American Museum of Natural History]] also opposed the Trade Center project, citing hazards the buildings would impose on [[Bird migration|migrating bird]]s.<ref>{{cite news |title=Big Trade Center Called Bird Trap |author=Knowles, Clayton |publisher=The New York Times |date=March 16, 1967}}</ref>

The structural engineering firm, Skilling, Helle, Christiansen, [[Leslie Robertson|Robertson]], worked to implement Yamasaki's design, developing the tube-frame structural system used in the buildings. The Port Authority's Engineering Department served as [[geotechnical engineering|foundation engineers]], Joseph R. Loring & Associates as [[electrical engineering|electrical engineers]], and Jaros, Baum & Bolles as [[mechanical engineering|mechanical engineers]]. [[Tishman Reality & Construction|Tishman Realty & Construction Company]] was the [[general contractor]] on the World Trade Center project. Guy F. Tozzoli, director of the World Trade Department at the Port Authority, and the Port Authority's Chief Engineer, Rino M. Monti, oversaw the project.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF | title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |chapter=Chapter 1 |date=September 2005 |pages=p. 1}}</ref>

===Structural design===
As an interstate agency, the Port Authority was not subject to local laws and regulations of the City of New York, including [[building code]]s. Nonetheless, the Port Authority required architects and structural engineers to follow the New York City building codes. At the time when the World Trade Center was planned, new building codes were being devised to replace the 1938 version that was in place. The structural engineers ended up following draft versions of the new 1968 building codes which incorporated "advanced techniques" in [[building design]].<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xxxviii |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>

The World Trade Center towers included many [[structural engineering]] innovations in [[skyscraper design and construction]], which allowed the buildings to reach new heights and become the [[List of tallest buildings in the world|tallest]] in the world. Traditionally, [[skyscraper]]s used a skeleton of [[column]]s distributed throughout the interior to support building loads, with interior columns disrupting the floor space. The tube-frame concept was a major innovation, allowing open floor plans and more space to rent. The buildings used high-strength, load bearing perimeter [[steel]] columns called [[truss#Vierendeel truss|Vierendeel trusses]], that were spaced closely together to form a strong, rigid wall structure. There were 59 perimeter columns, narrowly spaced on each side of the buildings. These were designed to provide support for virtually all lateral loads (such as wind loads) and to share the gravity loads with the core columns.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |format =PDF |date=September 2005 |chapter=Chapter 1 |pages=p. 6}}</ref> Structural analysis of major portions of the World Trade Center were computed on an [[IBM 1620]]<ref>R.E. Taylor, "Computers and the Design of the World Trade Center", ''J. Structural Division'', ASCE, vol. 92, ST-6, Dec. 1966, pp. 75-91.</ref>.
[[Image:Nistncstar1-1-fig2-4.png|thumb|right|Typical WTC architectural floor plan]]

The perimeter structure was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected together by [[wikt:spandrel|spandrel]] plates. The perimeter columns had a square cross section, 14 inches (36 cm) on a side, and were constructed of welded steel plate.<ref name="NIST-chapter1">{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |date=September 2005}}</ref> The thickness of the plates and grade of [[structural steel]] varied over the height of the tower, ranging from 36,000 to 100,000 pounds per square inch<ref>[[A36 steel]] has a nominal [[Yield (engineering)|yield strength]] of 36,000 to 100,000 pounds per square inch.</ref> (260 to 670 MPa). The strength of the steel and thickness of the steel plates decreased with height because they were required to support lesser amounts of building mass on higher floors.<ref name="NIST-chapter1"/> The tube-frame design required 40 percent less structural steel than conventional building designs.<ref name="steel">{{cite journal |author=American Iron and Steel Institute |title=The World Trade Center - New York City |journal=Contemporary Steel Design |volume=1(4) |year=1964 |publisher=American Iron and Steel Institute}}</ref> From floor #7 to the ground level and down to the foundation, the columns were spaced 10 feet (3 m) apart.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |date=September 2005 |pages=p. 10}}</ref> All columns were founded on [[bedrock]], which unlike Midtown Manhattan, where the bedrock is shallow, is at 65–85 feet (20–26 m) below the surface.<ref>{{cite journal |url=http://www.nae.edu/nae/bridgecom.nsf/weblinks/CGOZ-58NLJ9?OpenDocument |title=World Trade Center "Bathtub": From Genesis to Armageddon |journal=Bridges |author=Tamaro, George J. |date=Spring 2002 |volume=32(1)}}</ref>

The spandrel plates were welded to the columns to create the modular pieces off-site at the fabrication shop.<ref>{{cite book |author=National Construction Safety Team |url=http://wtc.nist.gov/NISTNCSTAR1CollapseofTowers.pdf |format =PDF |title=Final Report on the Collapse of the World Trade Center Towers |publisher=NIST |date=September 2005 |pages=p. 8}}</ref> The modular pieces were typically 52 inches (1.3 m) deep, and extended for two full floors and half of two more floors.<ref name="NIST-chapter1"/> Adjacent modules were bolted together, with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, and served to transmit [[shear stress]] between columns, thus allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.<ref name="NIST-chapter1"/>

The building's core housed the [[elevator]] and utility shafts, restrooms, three stairwells, and other support spaces. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m), and contained 47 steel columns running from the bedrock to the top of the tower.<ref name="NIST-chapter1"/> The columns tapered with height, and consisted of welded box-sections at lower floors and rolled wide-flange sections at upper floors. The core in 1 WTC was oriented with the long axis east to west, while that of 2 WTC was oriented north to south. All of the elevators were located in the core. Each building had three stairwells that were also located in the core, except on the [[mechanical floor]]s where they were located outside of the structural core.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 8 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>
[[Image:Wtc floor truss system.png|thumb|left|Schematic of composite floor truss system]]
The large, column-free space between the perimeter and core was bridged by pre-fabricated floor trusses. The floors supported their own weight, as well as [[live loads]], provided lateral stability to the exterior walls, and distributed wind loads among the exterior walls. The floors consisted of 4 inch (10 cm) thick lightweight [[concrete]] slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors. The trusses had a span of 60 feet (18.2 m) in the long-span areas and 35 feet (11 m) in the short span area.<ref name="NIST-chapter1"/> The trusses connected to the perimeter at alternate columns, and were therefore on 6 foot 8 inch (2.03 m) centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandrel plates with [[Viscoelasticity|viscoelastic]] dampers, which helped reduce the amount of sway felt by building occupants. The trusses supported a 4 inch thick (10 cm) lightweight concrete floor slab, with shear connections for composite action.<ref name="NIST-chapter1"/>

Hat [[trusses]] (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communications [[Antenna (radio)|antenna]] on top of each building.<ref name="NIST-chapter1"/> Only 1 WTC (north tower) actually had an antenna fitted, which was added in 1978.<ref>{{cite web |url=http://www.pbs.org/wgbh/amex/newyork/sfeature/sf_building.html |title=New York: A Documentary Film - The Center of the World (Construction Footage) |publisher = Port Authority / PBS |accessdate=2007-05-16}}</ref> The truss system consisted of six trusses along the long axis of core and four along the short axis. This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower.

===Wind effects===
The tube frame design using steel core and perimeter columns protected with sprayed-on fire resistant material created a relatively lightweight structure that would sway more in response to the wind, compared to traditional structures such as the [[Empire State Building]] that have thick, heavy [[masonry]] for fireproofing of steel structural elements.<ref>{{cite book |title=City in the Sky |author=Glanz, James and Eric Lipton |pages=p. 138 |publisher=Times Books |year=2003}}</ref> During the design process, [[wind tunnel]] tests were done at [[Colorado State University]] and at the [[National Physical Laboratory, UK|National Physical Laboratory]] in the [[United Kingdom|U.K.]] to establish design wind pressures that the World Trade Center towers could be subjected to and structural response to those forces.<ref>{{cite book |title=Design and Construction of Structural Systems (NCSTAR 1-1A) |publisher=National Institute of Standards and Technology |pages=p. 65 |author=Fanella, David A., Arnaldo T. Derecho, S.K. Ghosh |date=September 2005}}</ref> Experiments were also done to evaluate how much sway occupants could tolerate. Subjects were recruited for "free eye exams", while the real purpose of the experiment was to subject them to simulated building sway and find out how much they could comfortably tolerate.<ref>{{cite book |title=City in the Sky |author=Glanz, James and Eric Lipton |pages=p. 139-144 |publisher=Times Books |year=2003}}</ref> Many subjects did not respond well, experiencing [[dizziness]] and other ill effects. The chief engineer [[Leslie Robertson]] worked with Canadian engineer Alan G. Davenport to develop viscoelastic [[Damping|dampers]] to absorb some of the sway. These viscoelastic dampers, used throughout the structures at the joints between floor trusses and perimeter columns, along with some other structural modifications reduced the building sway to an acceptable level.<ref>{{cite book |title=City in the Sky |author=Glanz, James and Eric Lipton |pages=p. 160-167 |publisher=Times Books |year=2003}}</ref> Once built, high winds caused the upper floors to oscillate as much as 2 feet or more. This could be observed to a building occupant by watching a door ajar sway back and forth as on a ship at sea.

===Fire protection===
[[Fireproofing|Sprayed-fire resistant material]]s (SFRMs) were used to protect some structural steel elements in the towers, including all floor trusses and beams.<ref name="NCSTAR 1-1-p8">{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 8 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> [[Gypsum]] [[wallboard]] in combination with SFRMs, or in some cases gypsum wallboard alone, was used to protect core columns.<ref name="NCSTAR 1-1-p8"/> [[Vermiculite]] plaster was used on the interior-side and SFRMs on the other three sides of the perimeter columns for fire protection.<ref name="NCSTAR 1-1-p8"/> The 1968 New York City building codes were more lenient in some aspects of fire protection, such as allowing three exit stairwells in the World Trade Center towers, instead of six as required under older building codes.<ref name="NCSTAR 1-1-p153">{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 153 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>

The 1968 New York City building codes did not require [[Fire sprinkler|sprinkler]]s for [[high-rise]] buildings, except for underground spaces. In accordance with building codes, sprinklers were originally installed only in the underground parking structures of the World Trade Center.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 162 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> Following a major fire in February 1975, the Port Authority decided to start installing sprinklers throughout the buildings. By 1993, nearly all of Tower 2 [South Tower], and 85% of Tower 1 had sprinklers installed,<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. 163 |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> and the entire complex was retrofitted by 2001.<ref>{{cite book |title=Active Fire Protection Systems (NCSTAR 1-4) |publisher=National Institute of Standards and Technology |pages=p. 14 |author=Evans, David D., Richard D. Peacock, Erica D. Kuligowski, W. Stuart Dols, William L. Grosshandler |date=September 2005}}</ref>

==Construction==
In March 1965, the Port Authority began acquiring property at the World Trade Center site.<ref>{{cite news |title=Port Agency Buys Downtown Tract |author=Ingraham, Joseph C. |date=March 29, 1965 |publisher=The New York Times}}</ref> The Ajax Wrecking and Lumber Corporation was hired for the [[demolition]] work, which began on [[March 21]], [[1966]] to clear the site for construction of the World Trade Center.<ref name="gillespie-p61">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 61}}</ref>

[[Groundbreaking]] was on [[August 5]], [[1966]], marking the beginning of construction of the World Trade Center's foundations.<ref>{{cite news |title=Jackhammers Bite Pavement to Start Trade Center Job |date=August 6, 1966 |publisher=The New York Times}}</ref> The site of the World Trade Center was located on landfill, with the bedrock located 65 feet (20 m) below.<ref name="iglauer">{{cite news |title=The Biggest Foundation |author=Iglauer, Edith |date=November 4 1972 |publisher=The New Yorker}}</ref> In order to construct the World Trade Center, it was necessary to build the "bathtub", with the [[slurry wall]] along the [[West Street]] side of the site, to keep water from the Hudson River out. This method was used in place of conventional dewatering methods because lowering the [[groundwater table]] would cause large [[settlement (construction)|settlements]] of nearby buildings not built on [[deep foundation]]s.<ref>{{cite news |title=Tall Towers will Sit on Deep Foundations |last=Kapp |first=Martin S |publisher=Engineering News Record |date=July 9, 1964}}</ref> The slurry method involves digging a [[trench]], and as [[excavation]] proceeds, filling the space with a "slurry" mixture, composed of [[bentonite]] which plugs holes and keeps water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out. The "slurry" method was devised by Port Authority chief engineer, John M. Kyle, Jr. Towards the end of 1966, work began on building the [[slurry wall]], led by [[Montreal]]-based Icanda, a subsidiary of an Italian engineering firm, Impresa Costruzioni Opere Specializzate (I.C.O.S.).<ref name="gillespie-p68">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 68}}</ref> It took fourteen months for the slurry wall to be completed, which was necessary before excavation of material from the interior of the site could begin.<ref name="gillespie-p68"/> The original [[Downtown Hudson Tubes|Hudson Tubes]], which carried PATH trains into Hudson Terminal, remained in service as elevated [[tunnel]]s until 1971 when a new [[World Trade Center (PATH station)|PATH station]] was built.<ref>{{cite news |author=Carroll, Maurice |title=A Section of the Hudson Tubes is Turned into Elevated Tunnel |date=December 30, 1968 |publisher=The New York Times}}</ref>
[[Image:Wtc panynj 1973.jpg|thumb|right|200px|World Trade Center in 1973]]
[[Construction|Construction work]] began on the North Tower in August 1968 with construction beginning on the South Tower by January 1969.<ref name="pbstimeline">{{cite web |url=http://www.pbs.org/wgbh/amex/newyork/timeline/index.html |title=Timeline: World Trade Center chronology |publisher=PBS - American Experience |accessdate=2007-05-15}}</ref> In January 1967, $74 million in contracts were awarded to the [[PACCAR|Pacific Car and Foundry Company]], [[Laclede Steel Company]], [[U.S. Steel|Granite City Steel Company]], and [[Karl Koch Steel Consulting|Karl Koch Erecting Company]] to supply [[steel]] for the project.<ref name="nyt-1967jan24">{{cite news |title=Contracts Totaling $74,079,000 Awarded for the Trade Center |publisher=The New York Times |date=January 24, 1967}}</ref> The Port Authority chose to use many different steel suppliers, bidding on smaller portions of steel, rather than buy larger amounts from a single source such as [[Bethlehem Steel]] or [[U.S. Steel]] as a cost-saving measure.<ref name="gillespie-p83">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 83}}</ref> Karl Koch was also hired to do all the work of erecting the steel, and a contract for work on the aluminum facade was awarded to the [[Alcoa|Aluminum Company of America]].<ref name="nyt-1967jan24"/> [[Tishman Realty & Construction]] was hired in February 1967 to oversee construction of the project.<ref>{{cite news |title=Trade Center Job To Go To Tishman |author=Kihss, Peter |publisher=The New York Times |date=February 27, 1967}}</ref>

Extensive use of [[prefabrication|prefabricated]] parts for the perimeter framing and floor truss systems helped speed up the construction process and reduce costs, while providing greater [[quality control]].<ref name="steel"/> Steel components were freighted into a [[Penn Central Transportation|Penn Central]] yard in [[Jersey City, New Jersey|Jersey City]]. From there, they were brought in early morning hours through the [[Holland Tunnel]] to the construction site, and lifted into place by a [[Crane (machine)|crane]].<ref>{{cite news |title=Trade Center is Doing Everything Big |publisher=The New York Times |date=June 6, 1969 |author=Kaufman, Micheal T.}}</ref> Larger pieces were brought to the construction site by [[tugboat]]s.<ref name="gillespie-p88">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 88}}</ref> A special type of crane, suitable for constructing such tall buildings, that used [[hydraulics]] to lift components and provided its own power was used in construction of the World Trade Center. The Favco Standard 2700 Crane, manufactured by Favelle Mort Ltd. of [[New South Wales]], [[Australia]] was informally called a "[[kangaroo]] crane".<ref name="gillespie-p92">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 92-94}}</ref>

In 1970, tugboat workers went on [[Strike action|strike]], halting the transport of material to the construction site.<ref>{{cite news |title=300 Tugboats Idle as Men Walk Out for Doubled Wage |author=McFadden, Robert D. |date=February 2, 1970 |publisher=The New York Times}}</ref> The Port Authority attempted other means of transporting material, including via [[helicopter]]. When this method was tried, the helicopter lost its load of steel into the [[Kill Van Kull]].<ref name="gillespie-p91">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 91}}</ref> Some other mishaps occurred during the construction process, including disruption of [[telephone]] service in Lower Manhattan when telephone cables were crushed by [[pile driver]]s.<ref>{{cite news |author=Carroll, Maurice |title=Phones Disrupted by a Pile Driver |date=March 19, 1969 |publisher=The New York Times}}</ref> On [[March 16]], [[1970]], a [[propane]] gas explosion injured six workers, when a truck hit a propane tank.<ref>{{cite news |title=Propane Blast Hits Trade Center |author=Van Gelder, Lawrence |date=March 17, 1970 |publisher=The New York Times}}</ref> In all, 60 workers were killed in construction accidents while the World Trade Center was being built.<ref>{{cite web |url=http://www.pbs.org/americarebuilds/engineering/engineering_qfacts.html |title=America Rebuilds: Quick Facts |publisher=PBS |accessdate=2007-05-15}}</ref>

Construction of 1 World Trade Center (North Tower) was completed on [[December 23]], [[1970]], with 2 World Trade Center (South Tower) completed on [[July 19]], [[1971]].<ref name="pbstimeline"/> First tenants moved into the North Tower in December 1970, and into the South Tower in January 1972.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xxxvi |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> The buildings were dedicated on [[April 4]], [[1973]]; Tobin, who resigned the year before, was absent from the ceremonies.<ref name="Darton-chap6">Darton, Eric (1999) ''Divided We Stand: A Biography of New York's World Trade Center'', Chapter 6, Basic Books.</ref>

Building the World Trade Center involved excavating 1.2 million [[cubic yard]]s (917,000 [[Cubic metre|m³]]) of material.<ref name="gillespie-p71">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 71}}</ref> Rather than transporting this material at great costs out to sea or to landfills in [[New Jersey]], the fill material was used to expand the [[Manhattan]] shoreline across [[West Street]].<ref name="gillespie-p71"/> Work to demolish the [[pier]]s began on [[January 5]], [[1967]], including Pier 7 to Pier 11 which were all constructed around 1910.<ref>{{cite news |title=Demolition Begun on 5 City Piers |author=Horne, George |publisher=The New York Times |date=January 5, 1967}}</ref> The demolition work moved forward, despite conflicts between [[David Rockefeller]], Governor [[Nelson Rockefeller]], and Mayor [[John Lindsay]] regarding plans for Battery Park City.<ref>{{cite news |title=Conflicts Stall Landfill Plans |author=Roberts, Steven V. |publisher=The New York Times |date=January 17, 1967}}</ref> Landfill material from the [[World Trade Center]] was used to add land, and a cellular [[cofferdam]] was constructed to retain the material.<ref name="iglauer">{{cite news |url=http://www.newyorker.com/archive/content/articles/010924fr_archive02 |title=The Biggest Foundation |author=Iglauer, Edith |date=November 4 1972 |publisher=The New Yorker}}</ref> The result was a 700 foot (210 m) extension into the [[Hudson River]], running six blocks or 1,484 feet (450 m).<ref name="gillespie-p71"/> This land was a "gift" to New York City, allowing more [[tax]]-generating developments in [[Battery Park City, Manhattan|Battery Park City]].<ref>{{cite news |title=New York Gets $90 Million Worth of Land for Nothing |publisher=Engineering News Record |date=April 18, 1968}}</ref>

The original estimates put forth by the Port Authority had the costs for construction of the World Trade Center at $350 million — an optimistic figure.<ref name="gillespie-p70">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 70}}</ref> In December 1966, the Port Authority announced increased cost estimates, bringing the estimated total to $575 million.<ref name="gillespie-p69">{{cite book |author=Gillespie, Angus K. |year=1999 |title=Twin Towers: The Life of New York City's World Trade Center |publisher=Rutgers University Press |pages=p. 69}}</ref> This announcement brought criticism of the project from private real estate developers, the [[New York Times]], and others in New York City.<ref>{{cite news |title=Questions on the Trade Center |publisher=The New York Times |date=December 24, 1966}}</ref> The critics charged that the Port Authority figure was unrealistically low estimate, and they estimated the project would end up costing $750 million.<ref>{{cite news |title=Estimate Raised for Trade Center |author=Phillips, McCandlish |date=December 29, 1966 |publisher=The New York Times}}</ref> When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.<ref name="Cudahy">Cudahy, Brian J. (2002) ''Rails Under the Mighty Hudson: The Story of the Hudson Tubes, the Pennsy Tunnels, and Manhattan Transfer'', Chapter 3, Fordham University Press.</ref> The project was financed through [[Tax exemption|tax-exempt]] [[Bond (finance)|bond]]s issued by the Port Authority.<ref>{{cite news |author=Allan, John H. |title=Bonds: Port of New York Authority to Raise $100-Million |date=February 28, 1968 |publisher=The New York Times}}</ref>

==Other buildings==
The World Trade Center complex included four other, smaller buildings constructed during the 1970s. 3 World Trade Center was a 22-story building, which was home to the [[Marriott World Trade Center]]. It was designed by [[Skidmore, Owings and Merrill]] in 1978-79.<ref>{{cite book |author=McAllister, Therese, Johnathan Barnett, John Gross, Ronald Hamburger, Jon Magnusson |chapter=WTC3 |title=World Trade Center Building Performance Study |publisher=FEMA |date=May 2002}}</ref> [[4 World Trade Center]], [[5 World Trade Center]], and [[6 World Trade Center]] were all 8-9 story buildings that were designed by the same team as the Twin Towers, including Minoru Yamasaki, Emery Roth & Sons, and Skilling, Helle, Christiansen, Robertson.<ref>{{cite book |author=McAllister, Therese, Johnathan Barnett, John Gross, Ronald Hamburger, Jon Magnusson |chapter=WTC4, 5, and 6 |title=World Trade Center Building Performance Study |publisher=FEMA |date=May 2002}}</ref> A seventh building ([[7 World Trade Center]]) was built in the mid-1980s, just to the north of the main World Trade Center site. The 47-story building was designed by Emery, Roth & Sons, and constructed on top of a [[Con Edison]] power [[substation]].<ref>{{cite book |author=McAllister, Therese, Johnathan Barnett, John Gross, Ronald Hamburger, Jon Magnusson |chapter=WTC7 |title=World Trade Center Building Performance Study |publisher=FEMA |date=May 2002}}</ref>

==Modifications==
Over time, numerous structural modifications were made to suit the needs of tenants in the Twin Towers. Modifications were made in accordance with the Port Authority's ''Tenant Alteration Review Manual'' and were reviewed by the Port Authority to ensure the changes did not compromise structural integrity of the buildings. Oftentimes, openings were cut in the floors to allow new [[stairway]]s to be built to connect tenant floors. Some steel beams in the core were reinforced and strengthened to accommodate heavy live loads, such as large amounts of heavy files that tenants had on their floors.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xliv |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref>

Repairs to structural elements on the lower levels of 1 WTC [North Tower] were made following the [[1993 World Trade Center bombing]]. The greatest damage occurred on levels B1 and B2, with significant structural damage also on level B3.<ref>{{cite book |title=Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1) |publisher=National Institute of Standards and Technology |pages=p. xlv |author=Lew, H.S., Richard W. Bukowski, Nicholas J. Carino |date=September 2005}}</ref> Primary structural columns were not damaged, but secondary steel members experienced some damage.<ref>{{cite web |url=http://www.interfire.org/res_file/pdf/Tr-076.pdf |format =PDF |title=Experiences of the Chief Engineer of the Port Authority |author=Fasullo, Eugene |publisher=United States Fire Administration |accessdate=2007-05-15}}</ref> Floors that were blown out needed to be repaired, to restore the structural support they provided to columns.<ref>{{cite web |url=http://www.interfire.org/res_file/pdf/Tr-076.pdf |format =PDF |title=The World Trade Center Complex |author=Port Authority Risk Management Staff |publisher=United States Fire Administration |accessdate=2007-05-15}}</ref> The slurry wall was in peril following the bombing and loss of the floor slabs which provided lateral support to counteract pressure from Hudson River water on the other side.<ref name="ennala">{{cite journal |author=Ramabhushanam, Ennala and Marjorie Lynch |title=Structural Assessment of Bomb Damage for World Trade Center |journal=Journal of Performance of Constructed Facilities |volume=8(4) |pages=229-242}}</ref> The [[refrigeration]] plant on sublevel B5, which provided [[air conditioning]] to the entire World Trade Center complex, was heavily damaged and replaced with a temporary system for the summer of 1993.<ref name="ennala"/> The [[fire alarm]] system for both towers needed to be replaced, after critical wiring and signaling in the original system was destroyed in the 1993 bombing. Installation of the new system took years to complete, and replacement of some components was still underway at the time of the [[September 11, 2001 attacks]].<ref>{{cite book |title=Active Fire Protection Systems (NCSTAR 1-4) |publisher=National Institute of Standards and Technology |pages=p. 44 |author=Evans, David D., Richard D. Peacock, Erica D. Kuligowski, W. Stuart Dols, William L. Grosshandler |date=September 2005}}</ref>

==See also==
* [[Collapse of the World Trade Center]]
* [[Freedom Tower]]
* [[150 Greenwich Street]]
* [[175 Greenwich Street]]
* [[200 Greenwich Street]]
* [[Plans to rebuild the World Trade Center]]
* [[Philippe Petit]], who wirewalked between the two towers

==References==
{{reflist|2}}

==External links==
* [http://www.pbs.org/wgbh/amex/newyork/sfeature/sf_building.html New York: A Documentary Film - The Center of the World] - ''Building the World Trade Center'', an 18-minute film, with construction footage, produced by the Port Authority in 1983
* [http://www.skyscraper.org/WHAT%27S_UP/WTC_DOSSIER/wtc.htm World Trade Center] - Skyscraper Museum
* {{Cite web
| title = Corus in construction - Systems evolution
| accessdate = 2007-05-14
| url = http://corusconstruction.com/en/reference/teaching_resources/architectural_studio_reference/design/tall_building_designs/systems_evolution/
}}
* [http://wtc.nist.gov/ NIST and the World Trade Center]
* [http://www.ericdarton.net/ New York's World Trade Center - A Living Archive] - by author, Eric Darton
* [http://www.antiqueradio.com/Sep02_RadioRow_Steinhardt.html The Death of New York's Radio Row], by Syd Steinhard - Downtown Express

{{WTC navigation}}
{{Featured article}}
[[Category:World Trade Center]]
[[Category:Building projects|World Trade Center]]

IBM 729

2006-12-13T19:13:14Z

RTC: character mode data and binary mode data used opposite parity, allowing detection of incorrect format of tape. I just don't recall which was odd and which was even right now.

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|280px|A bank of IBM 729 tape drives.]]
[[Image:Tapesticker.jpg|thumb|Reel of tape showing beginning-of-tape reflective marker.]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. It was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[foot (unit of length)|feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]].

The tape had [[IBM 7 Track|seven parallel tracks]], six for data and one to maintain [[parity]]. Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch. At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 [[punch card]]s.

==Models==
===729 I===
The IBM 729 I was introduced for the [[IBM 709]] and [[IBM 705|IBM 705 III]] computers, looked identical to the [[IBM 727]], and used [[vacuum tube]]s. The main improvement was the use of a dual gap head permitting write verify.

===729 II===
The IBM 729 II was introduced for the [[IBM 700/7000 series#IBM 7000 series, transistors, 1960s|IBM 7000 series]] computers, introducing a new cabinet style and [[transistor]]ized circuitry. Supported dual density (200, 556).

===729 III===
High speed (112.5 in/s) single density (556).

===729 IV===
High speed (112.5 in/s) dual density (200, 556).

===729 V===
High density (800).

===729 VI===
High speed (112.5 in/s) high density (800).

==Reference==
* IBM 709 Data Processing System, Form A22-6501-0

==External link==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|729]]
[[Category:History of computing hardware]]

IBM 729

2006-07-20T06:06:38Z

RTC: /* External link */

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|IBM 729s in action]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. It was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) [[magnetic tape]] up to 2400 [[feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]].

[[Image:Tapesticker.jpg|thumb|left|Reel of tape showing beginning-of-tape reflective marker.]]
The tape had seven parallel tracks, six for data and one to maintain odd [[parity]]. Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a removable plastic ring in the back of the tape reel. A gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later 729 models supported 556 and 800 characters/inch.

==Reference==
* IBM 709 Data Processing System, Form A22-6501-0

==External link==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

{{Magnetic tape data formats}}

[[Category:IBM storage devices|729]]
[[Category:History of computing hardware]]

IBM 729

2006-07-20T05:28:54Z

RTC: /* External link */

CDC 6600

2006-07-14T02:43:17Z

RTC: /* Description */ sp

The '''CDC 6600''', a member of the [[CDC 6000 series]], was a [[mainframe]] [[computer]] from [[Control Data Corporation]], first manufactured in [[1964]]. It is generally considered to be the first successful [[supercomputer]], outperforming the fastest machines of the era by about three times. It remained the world's fastest computer from 1964 to [[1969]], when it relinquished that status to its successor, the [[CDC 7600]].

The basic organization of the CDC 6600 was also used to develop the simpler (and slower) [[CDC 6400]], and later a version containing two 6400 processors known as the [[CDC 6500]]. These machines were instruction-compatible with the 6600, but ran slower due to a different processor design. The [[CDC 7600]] was originally to be compatible as well, starting its life as the CDC 6800, but during the design compatibility was dropped in favour of outright performance.

==History and impact==
CDC's first products were based on the machines designed at [[Engineering Research Associates|ERA]], which [[Seymour Cray]] had been asked to update after moving to CDC. After an experimental machine known as the '''Little Character''', they delivered the [[CDC 1604]], one of the first commercial [[transistor]]-based computers, and one of the fastest machines on the market. Management was delighted, and made plans for a new series of machines that were more tailored to business use; they would include instructions for character handling and record keeping for instance. Cray was not interested in such a project, and set himself the goal of producing a new machine that would be 50 times faster than the 1604. When asked to complete a detailed report on future plans at one and five years into the future, he wrote back that his five year goal was "to produce the largest computer in the world", and his one year plan "to be one-fifth of the way".

Taking his core team to new offices nearby the original CDC headquarters, they started to experiment with higher quality versions of the "cheap" transistors Cray had used in the 1604. After much experimentation they found that there was simply no way the [[germanium]]-based transistors could be run much faster than the 1604. In fact the "business machine" that management had originally wanted, now forming as the [[CDC 3000]] series, pushed them about as far as they could go. Cray then decided the solution was to work with the then-new [[silicon]]-based transistors from [[Fairchild Semiconductor]], which were just coming onto the market and offered dramatically improved switching performance.

During this period CDC grew from a startup to a large company. Cray became increasingly frustrated with what he saw as ridiculous management requirements. Things became considerably more tense in 1962 when the new CDC 3600 started to near production quality, and appeared to be exactly what management wanted, when they wanted it. Cray eventually told CDC's CEO, [[William Norris]] that something had to change, or he would leave the company. Norris felt he was too important to lose, and gave Cray the green light to set up a new lab wherever he wanted.

After a short search, Cray eventually decided to return to his home town of [[Chippewa Falls, WI]], where he purchased a block of land and started up a new lab. Although this process introduced a fairly lengthy delay in the design of his new machine, once in the new lab things started to progress quickly. By this time the new transistors were becoming quite reliable, and modules built with them tended to work properly on the first try. Working with Jim Thornton, who was the system architect and the 'hidden genius' behind the 6600, the machine soon took form.

About 50 CDC 6600's were sold over the machine's lifetime. Most of these went to various [[nuclear bomb]]-related labs, although some found their way into university computing labs as well. Cray immediately turned his attention to its replacement, this time setting a goal of 10 times the performance of the 6600, delivered as the [[CDC 7600]]. The later [[CDC Cyber]] 70 and 170 computers were much like the CDC 6600.

==Description==
Typical machines of the era used a single complex [[Central processing unit|CPU]] to drive the entire system. A typical program would first load data into memory (often using pre-rolled library code), process it, and then write it back out. This required the CPU's to be fairly complex in order to handle the complete set of instructions they needed to run. A complex CPU implied a large CPU, introducing signalling delays while information flowed between the individual modules making it up. These delays set a maximum upper limit on performance, the machine could only operate at a cycle speed that allowed the signals time to arrive at the next module.

Cray took another approach. At the time, CPUs generally ran slower than the [[main memory]] they were attached to. For instance, a processor might take 15 cycles to multiply two numbers, while each memory access took only one or two. This meant there was a significant time where the main memory was idle. It was this idle time that the 6600 extracted.

Instead of trying to make the CPU handle all the tasks, the 6600's handled math and logic only. This resulted in a much smaller CPU, which in turn allowed it to operate at a higher clock speed. Combined with the faster switching speeds of the silicon transistors, the new CPU design would easily outperform anything then available. The new design ran at a clock speed of 100ns (10 MHz), about ten times that of other machines on the market. Additionally the simple processor also made operations themselves faster; for instance, the CPU could complete a multiplication in only three cycles.

Of course, being simple, it wouldn't be able to do much, either. In order to handle all of the normal "housekeeping" tasks a typical CPU was asked to handle memory and [[input/output]] as well. Cray removed these instructions from the main CPU, and instead implemented them in separate hardware. By allowing the CPU and I/O to operate in parallel, the design effectively doubled the performance of the machine.

Of course this would also make the machine dramatically more expensive. Key to the 6600's design was to make the I/O processors, known as '''Peripheral Processors''' or ''PP''s, as simple as possible. The PPs were based on the simple 12-bit [[CDC 160A]], which ran much slower than the CPU, gathering up data and "squirting" it into main memory at high speed via dedicated hardware. To make up for their slow speed, the 6600 included ten PP's in total.

The machine as a whole operated in a fashion known as "'''barrel and slot'''", the "barrel" referring to the ten PP's, and the "slot" the main CPU. For any given slice of time, one PP was given control of the CPU, asking it to complete some task (if required). Control was then handed off to the next PP in the barrel. Programs were written, with some difficulty, to take advantage of the exact timing of the machine to avoid any "dead time" on the CPU. With the CPU running much faster than normal each memory access required ten of these faster cycles to complete, so by using ten PP's, each PP was guaranteed one memory access per machine cycle.

The 10 PP's were implemented "'''virtually'''" - there was CPU hardware only for a single PP. This CPU hardware was shared and operated on 10 PP register sets which represented each of the 10 PP "'''states'''" (not unlike software tasking/threading). The "'''PP register barrel'''" would "'''rotate'''", with each PP register set presented to the "'''slot'''" which the actual PP CPU occupied. The shared CPU would execute all or some portion of a PP's instruction whereupon the barrel would rotate again, presenting the next PP's register set (state). Multiple rotations of the barrel were needed to complete an instruction. I believe a complete barrel rotation occurred in 1000 nanoseconds (100 nanoseconds per PP).

The basis for the 6600 CPU is what we would today refer to as a [[RISC]] system, one in which the processor is tuned to do instructions which are comparatively simple and have limited and well defined access to memory. The philosophy of many other machines was toward using instructions which were complicated — for example, a single instruction which would fetch an operand from memory and add it to a value in a register. In the 6600, loading the value from memory would require one instruction, and adding it would require a second. While slower in theory due to the additional memory accesses, the PPs offloaded this expense. This simplification also forced programmers to be very aware of their memory accesses, and therefore code deliberately to reduce them as much as possible.

===The Central Processor (CP)===
The Central Processor, or CP, has eight general purpose 60-[[bit]] [[processor register|registers]] X0 through X7, eight 18-bit address registers A0 through A7, and eight 18-bit scratchpad registers B0 through B7 (typically used for array indexing, with B0 permanently set to zero). Additional registers used for bookkeeping (such as the scoreboard register) are not accessible to the programmer. Additional registers (such as RA and FL) can only be loaded through the [[operating system]]. The CP has no instructions for input and output, which is accomplished through Peripheral Processors (below). In keeping with the RISC "load/store" philosophy, there are no instructions to read or write from/to core memory. All memory accesses are performed through loading an address into the A registers; loading A1 through A5 with an address would cause the data word at that location to be read into the corresponding X register (X1 through X5), while loading an address into A6 or A7 would cause register X6 or X7 to be written out to memory at that address. (Registers X0 and A0 were not involved in load/store operations this way). A separate hardware load/store unit handled the actual data movement independent of the operation of the instruction stream, allowing other operations to complete while memory was being accessed, which required (best case) eight cycles. In modern designs this sort of operation is normally supported directly by load/store instructions, which are given an explicit memory location to read or write, instead of the address registers used in the 6600. Floating-point operations were given pride of place in this [[Computer architecture|architecture]]: the CDC 6600 (and kin) stand virtually alone in being able to execute a 60-bit [[floating point]] multiplication faster than a program branch.

The CP included several parallel functional units, allowing multiple instructions to be worked on at the same time. Today this is known as a [[superscalar]] design, while at the time it was simply "unique". The system read and decoded instructions from memory as fast as possible, generally faster than they could be completed, and fed them off to the units for processing. The units included two floating point multipliers, a divider, an adder and "long" adder, two incrementers, a shifter, a boolean logic unit and a branch unit.

Previously executed instructions went into an eight-word [[Pipeline (computer)|pipeline]] (officially called a "stack") kept in onboard CP registers. Since the 15-bit instructions were packed four to a word, the system could pick any one of up to 32 previous instructions to run depending on which units were free. The pipeline was always flushed by an unconditional jump; it was sometimes faster (and would never be slower) than a ''conditional'' jump. The system used a 10 megahertz clock, but used a four-phase signal to match the four-wide instructions, so the system could at times effectively operate at 40 MHz. A floating point multiply took about three cycles, while a divide took about ten, and the overall performance considering memory delays and other issues was about 1 [[MFLOPS]]. Using the best available compilers, late in the machine's history, [[FORTRAN]] programs could expect to maintain about 0.5 MFLOPS.

===Memory organization===


User programs are restricted to use only a portion of contiguous core memory. The portion of memory the program has access to is controlled by the '''RA''' (Relative Address) and '''FL''' (Field Length) registers, and when a user program tries to read or write a word in central memory at address '''a''', the processor will first check that a is between 0 and FL-1. If this passes, the processor will access the word in central memory at address RA+a. This process is known as [[logical address translation]]; each user program sees core memory as a contiguous block of FL words starting at address 0, while in fact the program may be anywhere in the physical memory. Using this technique, each user program can be moved around in core memory by the operating system, as long as the RA register reflects its position in memory. A user program trying to access memory outside the allowed range will trigger an error, and will be terminated by the operating system. When this happens, a [[core dump]] will be output in a file, allowing the developer a way to know what happened. However, in contrast to [[virtual memory]] systems, the entirety of a process addressable space must be in core memory.

The [[CDC 6000 series]] could also be configured with an optional Extended Core Storage (ECS) system. ECS was composed of core memory, but both larger and slower than the core memory used for central (and PP) memory. A 6000 CPU could directly perform block memory transfers between a users program and the ECS unit. Wide data paths were used, so this was a very fast operation. Memory bounds were maintained in a similar manner as central memory - with a RA/FL mechanism maintained by the operating system. ECS could be used for a variety of purposes, including containing user data arrays that were too larger for central memory, holding often-used files, swapping, and even as a communication path in a multi-mainframe complex.

===Peripheral Processors (PPs)===
To handle the 'household' tasks which other designs put in the CPU, Cray included ten other processors, based partly on his earlier computer, the [[CDC 160A]]. These machines, called Peripheral Processors, or PPs, were full computers in their own right, but were tuned to performing [[Input/output|I/O]] tasks and running the operating system. One of the PP's was in overall control of the machine, including control of the program running on the main CPU, while the others would be dedicated to various I/O tasks. When the program needed to perform some sort of I/O, it instead loaded a small program into one of these other machines and let it do the work. The PP would then inform the CPU when the task was complete with an interrupt.

Each PP included its own memory (up to 4096 12-bit words), both for I/O buffering as well as program storage, but the execution units were shared by 10 PPs, in a configration called the [[Barrel processor|Barrel and slot]]. This meant that the execution units (the "slot") would execute one instuction cycle from the first PP, then one instruction cycle from the second PP, etc. in a round robin fashion. This was done both to reduce costs, and because access to CP memory required 10 PP clock cycles: when a PP accesses CP memory, the data is available next time the PP receives its slot time.

===Wordlengths, characters===
The central processor had 60-bit words, whilst the peripheral processors had 12-bit words. CDC used the term "byte" to refer to 12-bit entities used by peripheral processors; characters were 6-bit, and central processor instructions were either 15 bits, or 30 bits with a signed 18-bit address field, the latter allowing for a directly addressable memory space of 128K words of central memory (converted to modern terms, with 8-bit bytes, this is 0.94 megabytes). The signed nature of the address registers limited an individual program to 128K words. (Later CDC 6000-compatible machines could have 256K or more words of central memory, budget permitting, but individual user programs were still limited to 128K words of CM.) Central processor instructions started on a word boundary when they were the target of a jump statement or subroutine return jump instruction, so no-operations were sometimes required to fill out the last 15, 30 or 45 bits of a word.

The 6-bit characters, called [[display code]], could be used to store up to 10 characters in a word. They permitted a character set of 64 characters, which is enough for all upper case letters, digits, and some punctuation. Certainly, enough to write [[FORTRAN]], or print financial or scientific reports. There were actually two variations of the [[display code]] character sets in use, 64-character and 63-character. The 64-character set had the disadvantage that two consecutive ':' (colon) characters might be interpreted as the end of a line if they fell at the end of a 10-byte word. A later variant, called 6/12 [[display code]], was also used in the KRONOS and NOS timesharing systems to allow full use of the [[ASCII]] character set in a manner somewhat compatible with older software.

With no byte addressing instructions at all, code had to be written to pack and shift characters into words. The very large words, and comparatively small amount of memory, meant that programmers would frequently economise on memory by packing data into words at the bit level.

It is interesting to note that due to the large word size, and with 10 characters per word, it was often faster to process words full of characters at a time - rather than unpacking/processing/repacking them. For example, the CDC [[COBOL]] compiler was actually quite good at processing decimal fields using this technique. These sorts of techniques are now commonly used in the 'multi-media' instructions of current processors.

===Physical design===
The machine was built in a plus-sign-shaped cabinet with a pump and heat exchanger in the outermost 18 inches of each of the 4 arms. Cooling was done with [[Freon]] circulating within the machine and exchanging heat to an external chilled water supply. Each arm could hold 4 chassis, each about 8 inches thick, hinged near the center, and opening a bit like a book. The intersection of the "plus" was filled with cables which interconnected the chassis. The chassis were numbered from 1 (containing all 10 PPUs and their memories, as well as the rather minimal I/O channels) to 16. The main memory for the CPU was spread over many of the chassis.

The logic of the machine was packaged into modules about 2.5 inches square and about an inch thick. Each module had a connector (roughly 20 pins in each of 2 vertical rows) on one edge, and 6 test points on the opposite edge. The module was placed between two aluminum cold plates to remove heat. The module itself consisted of two parallel printed circuit boards, with components mounted either on one of the boards or between the two boards. This provided a very dense, if somewhat difficult to repair, package with good heat removal that was known as [[Cordwood construction#Other meanings|cordwood packaging]].

==Operating system and programming==

If there was a sore point with the 6600 it was the [[operating system]] support, which took entirely too long to work out.

The machines originally ran a very simple job-control system known as '''COS''', the '''''C'''hippewa '''O'''perating '''S'''ystem'', which was quickly "thrown together" based on the earlier [[CDC 3000]] operating system in order to have something running to test the systems for delivery. However the machines were intended to be delivered with a much more powerful system known as '''SIPROS''', for '''''SI'''multaneous '''PR'''ocessing '''O'''perating '''S'''ystem'', which was being developed at the company's System Sciences Division in [[Los Angeles]]. Customers were impressed with SIPROS's feature list, and many had SIPROS written into their delivery contracts.

SIPROS turned out to be a major fiasco. Development timelines continued to slip, costing CDC major amounts of profit in the form of delivery delay penalties. After several months of waiting with the machines ready to be shipped, the project was eventually cancelled. Luckily the programmers who had worked on COS had little faith in SIPROS (likely due largely to [[not invented here]] syndrome) and had continued working on it. Many customers eventually took delivery of their systems with this system instead, now known as '''SCOPE''' ('''''S'''upervisory '''C'''ontrol '''O'''f '''P'''rogram '''E'''xecution'').

However it was a third system, '''MACE''', which allowed the system to reach its potential. Written largely by a single programmer in the off-hours when machines were available, MACE squeezed every possible cycle out of the design for maximum performance. While its feature set was similar to the simple CHOPS/SCOPE, it ran many times faster. MACE was never an official product, although many customers were able to wrangle a copy from the company.

MACE was later used as the basis of '''KRONOS''', originally a request by a customer who wanted to use their 6400 as the basis of a [[time sharing]] system. SCOPE was considered too slow to work well in this fashion, so MACE was instead adapted and became completely "official" when it was released in 1967. A further development added in any missing features from SCOPE into KRONOS to produce '''NOS''', the '''''N'''etwork '''O'''perating '''S'''ystem''. NOS was ''the'' operating system for all CDC machines, a fact CDC promoted heavily, so when a few SCOPE customers refused to switch to NOS, they simply renamed it NOS/BE, and were able to claim that everyone was thus running NOS.

==References==
*Grishman, Ralph (1974). ''Assembly Language Programming for the Control Data 6000 Series and the Cyber 70 Series''. New York, NY: Algorithmics Press.
*[http://ed-thelen.org/comp-hist/CDC-6600-R-M.html#TOC/ CONTROL DATA 6400/6500/6600 COMPUTER SYSTEMS Reference Manual]
*Thornton, J. (1970). ''Design of a Computer -- The Control Data 6600''. Glenview, IL: Scott, Foresman and Co.

==See also==
* [[CDC 6000 series]]

==External links==
*[http://research.microsoft.com/~gbell/Computer_Structures__Readings_and_Examples/00000509.htm Parallel operation in the Control Data 6600, James Thornton]
*[http://research.microsoft.com/users/gbell/craytalk/sld001.htm Presentation of the CDC 6600 and other machines designed by Seymour Cray] – by C. [[Gordon Bell]] of Microsoft Research (formerly of DEC)

[[Category:CDC hardware|6600]]
[[Category:Supercomputers]]

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Game Designer

2006-06-08T22:45:32Z

RTC: /* History */

A '''game designer''' is a person who designs [[game|games]]. The term normally refers to a person who designs [[Computer and video games|computer or video games]], but it also refers to one who designs traditional games, such as [[board game]]s.

==Video and computer game designer==
[[Image:ScoobyDooGameDesign.jpg|thumb|This early version of the [[design document]] for ''[[Scooby Doo: Mystery of the Fun Park Phantom]]'' shows the dynamic nature of game design. As the cover of the 100+ page design document shows, it was originally planned to be called ''Scooby Doo: The Mystery of the Gobs o' Fun Ghoul''.]]
A video or computer game designer develops the layout, concept and [[gameplay]], the [[game design]] of a video or computer game. This may include playfield design, specification writing, and entry of numeric properties that balance and tune the gameplay. A game designer works for a [[video game developer|developer]] (which may additionally be the game's [[video game publisher]]). This person usually has a lot of [[writer|writing]] experience and may even have a degree in writing or a related field (such as [[English language|English]]). This person's primary job function is writing, so the more experience they have with the activity, the better. Some [[artist|art]] and [[programmer|programming]] skills are also helpful for this job, but are not strictly necessary. Game designers often have studied relevant liberal arts such as [[psychology]], [[sociology]], [[drama]], or [[philosophy]]. Due to the increasing complexity of the game design process, many young game designers may also come from a [[computer science]] or other computer engineering background.

In the [[video game industry]], the job of game designer is one of the hardest to obtain. It is not easy, though many people think they "have what it takes" to perform this job. Almost everyone in the game industry has what they believe is a "killer game" concept and is waiting for the opportunity to develop the game. As a game designer, they may get the opportunity to develop that game concept, so competition is usually very high.

Since a video game publisher may invest millions of [[dollar]]s towards a game's development, it is easy to understand why they choose game designers carefully—one or two poor game concepts could end up costing them millions of dollars of revenue and could even risk [[bankruptcy|bankrupting]] the company. For this reason, game publishers usually choose game designers who have a proven track record with several hit games under their belts. Less seasoned designers may be assigned to low profile games that have budgets in the low tens of thousands.

===History===
The first video games were designed in the [[1960s]] and [[1970s]] by programmers for whom creating games was a [[hobby]], since there was no way to sell them or earn money from creating games. Some were designed by electrical engineers as exhibits for visitors to computer labs ([[OXO]], [[Tennis for Two]]), others by college students who wrote games for their friends to play ([[Spacewar!]], [[Star Trek (text game)|Star Trek]], [[Dungeon (computer game)|Dungeon]]).

Some of the games designed during this era, such as [[Zork]], [[Baseball (computer game)|Baseball]], [[Air Warrior|Air]] and [[Colossal Cave Adventure|Adventure]] later made the transition with their game designers into the early [[video game industry]].

Early in the [[history of computer and video games|history of video games]], game designers were often the [[lead programmer]] or the ''only'' programmer for a game, and this remained true as the video game industry dawned in the 1970s. This person also sometimes comprised the entire art team. This is the case of such noted designers as [[Sid Meier]], [[Chris Sawyer]] and [[Will Wright]]. A notable exception to this policy was [[Coleco]], which from its very start separated the function of design and programming.

As games became more complex and [[home computer|computers]] and [[video game console|console]]s became more powerful (allowing more features), the job of game designer became a separate job function, with the lead programmer splitting his time between the two functions, moving from one role to the other. Later, game complexity escalated to the point where it required someone who concentrated solely on game design. Many early veterans chose the game design path eschewing programming and relegating those tasks to others.

Today, it is rare to find a video or computer game where the principal programmer is also the principal designer, except in the case of [[casual game]]s, such as ''[[Tetris]]'' or ''[[Bejeweled]]''. With very complex games, such as [[MMORPG]]s, or a big budget action or sports title, designers may number in the dozens. In these cases, there are generally one or two principal designers and many junior designers who specify subsets or subsystems of the game. In larger companies like [[Electronic Arts]], each aspect of the game (control, level design or vehicles) may have a separate producer, lead designer and several general designers.

===Notable video and computer game designers===

* [[Danielle Bunten Berry]], of the seminal ''[[M.U.L.E.]]'' and ''[[The Seven Cities of Gold (game)|The Seven Cities of Gold]]''.
* [[Marc Blank]], Co-designer of ''[[Zork]]'', co-founder of [[text adventure]] publisher [[Infocom]].
* [[Bill Budge]], ''[[Pinball Construction Set]]'', designer who anchored launch of [[Electronic Arts]].
* [[Chris Crawford (game designer)| Chris Crawford]], creator of ''[[Balance of Power (computer game)|Balance of Power]]'' and the founder of the [[Game Developer's Conference]].
* [[Don Daglow]], designer of ''[[Dungeon (computer game)|Dungeon]]'', ''[[Utopia (video game)|Utopia]]'', ''[[Earl Weaver Baseball]]'', and the original ''[[Neverwinter Nights (AOL game)|Neverwinter Nights]]''.
* [[Jon Freeman]], designer of the ''[[Archon (computer game)|Archon]]'' series of games.
* [[Richard Garriott]] (Lord British), developer of the ''[[Ultima]]'' series of games.
* [[Ron Gilbert]], creator of ''[[Maniac Mansion]]'' and the [[Monkey Island series|''Monkey Island'' series]]''.
* [[Stieg Hedlund]], designer of the ''Diablo'' series
* [[Hideo Kojima]], creator of the ''[[Metal Gear Solid]]'' series.
* [[Jordan Mechner]], designer of ''[[Prince of Persia]]'', ''[[Karateka (computer game)|Karateka]]'', and ''[[The Last Express]]''.
* [[Sid Meier]] of ''[[Civilization computer game|Civilization]]'' and ''[[Railroad Tycoon]]'' fame.
* [[Shigeru Miyamoto]] of ''[[Donkey Kong]]'', ''[[The Legend of Zelda]]'' and ''[[Super Mario]]'' series.
* [[Peter Molyneux]] of the ''[[Populous]]'' series, ''[[Black and White (computer game)|Black and White]]'' and ''[[Theme Park (game)|Theme Park]]'' among others.
* [[Scott Orr]], Designer of original version of ''[[Madden NFL]]'', many other sports titles.
* [[Brian Reynolds]], ''[[Civilization II]]'', ''[[Sid Meier's Alpha Centauri]]'' and ''[[Rise of Nations]]''.
* [[John Romero]] of ''[[Wolfenstein 3D]]'', the ''[[Doom]]'' and ''[[Quake]]'' series and [[game engine]]s.
* [[Hironobu Sakaguchi]] of the popular ''[[Final Fantasy]]'' series.
* [[Tim Schafer]], creator of ''[[Grim Fandango]] '' and ''[[Psychonauts]]''.
* [[Bruce Shelley]], co-creator of ''[[Age of Empires]]'' series and ''[[Civilization computer game|Civilization]]''
* [[Warren Spector]], ''[[System Shock]]'', ''[[Deus Ex]]'', ''[[Thief (computer game)|Thief, and Thief: Deadly Shadows]]'' series.
* [[Jordan Weisman]], Founder of [[FASA|FASA Interactive]], co-creator of ''[[BattleTech]]'' and ''[[MechWarrior]]''
* [[Roberta Williams]], designer of ''[[King's Quest]]'' and several other computer game series.
* [[Will Wright]], designer of ''[[SimCity]]'' and ''[[The Sims]]''.

==Notable game designers of non-video games==
* [[Frank Chadwick]] - Previous publisher of [[GDW]] and designer of over 50 war and role-playing games, including ''[[Twilight 2000]]'' and the ''[[Assault (game)|Assault]]'' series
* [[Jim Dunnigan]] - Previous publisher of [[SPI Games]] and designer of over 100 wargames, including the ''PanzerBlitz/Panzer Leader'' system
* [[Richard Garfield]] - [[collectible card game]] (''[[Magic: The Gathering]]'') and [[board game]] designer.
* [[Gary Gygax]] and [[David Arneson]] - creators of ''[[Dungeons & Dragons]]''
* [[Steve Jackson (US)|Steve Jackson]] - Designer of ''[[Ogre (game)|Ogre]]'', ''[[The Fantasy Trip]]'', ''[[Car Wars]]'', ''[[GURPS]]'', ''[[Hacker (card game)|Hacker]]'', ''[[Illuminati (game)|Illuminati]]'' and others.
* [[Reiner Knizia]] - prolific designer of [[German-style board game]]s who designed 6 of the top 20 games on the [[Internet Top 100 Games List]].
* [[Alan R. Moon]] - prolific designer of [[German-style board game]]s including [[Elfenland]] and [[Ticket to Ride]].
* [[Charles S. Roberts]] - Designer of first commercial board wargame (''[[Tactics II]]'') and founder of [[Avalon Hill]].

==See also==
* [[List of game designers]]
* [[List of video game designers]]

==External links==
* [http://www.sloperama.com/advice.html Tom Sloper's game biz advice], from the game design veteran, including lessons on being a game designer

===Newsgroups===
* [http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&group=comp.games.development.design comp.games.development.design via Google Groups]
* [http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&group=rec.games.design rec.games.design via Google Groups]

{{vg-industry}}

[[Category:Game designers| ]]
[[Category:Computer game design]]
[[Category:Art and design workers]]

[[ja:ゲームデザイナー]]
[[pl:Projektant gier]]

Tombigbee River

2006-02-22T22:26:24Z

RTC: rv - according to Google this is correct spelling, although it finds both spellings

The '''Tombigbee River''' is a tributary of the [[Mobile River]], approximately 400 mi (644 long), in the [[U.S. states]] of [[Mississippi]] and [[Alabama]]. It is one of two major rivers, along with the [[Alabama River]], that unite to form the short Mobile River before it empties into [[Mobile Bay]] on the [[Gulf of Mexico]]. The Tombigbee watershed encompasses much of the rural [[coastal plain]] of western Alabama and northeastern Mississippi, flowing generally southward. The river provides one of the principal routes of commercial navigation in the southern United States, navigable along much of its length through locks and connected in its upper reaches to the [[Tennessee River]] via the [[Tennessee-Tombigbee Waterway]].

==Description==
The river begins in northeastern Mississippi in [[Itawamba County, Mississippi|Itawamba County]]. Historically, the beginning of the river was in northern [[Monroe County, Mississippi|Monroe County]], by the confluence of and [[Town Creek (Mississippi)|Town Creek]] (also known as West Fork Tombigbee River) and [[East Fork Tombigbee River]]. Today, however, what was once known as the east fork is now designated as the Tombigbee itself.

It flows south through [[Aberdeen Lake (Mississippi)|Aberdeen Lake]] near [[Aberdeen, Mississippi|Aberdeen]], and [[Columbus Lake (Mississippi)|Columbus Lake]] near [[Columbus, Mississippi|Columbus]]. It flows through [[Aliceville Lake]] on the Mississippi-Alabama border, then generally SSE across western Alabama in a highly [[meander]]ing course, past [[Gainesville, Alabama|Gainesville]] and [[Demopolis, Alabama|Demopolis]], where it is joined from the northeast by the [[Black Warrior River]]. South of Demopolis it flows generally south across southwestern Alabama, past [[Jackson, Alabama|Jackson]]. It joins the Alabama from the north on the [[Mobile County, Alabama|Mobile]]-[[Baldwin County, Alabama|Baldwin]] county line, approximately 30 mi (48 km) north of [[Mobile, Alabama|Mobile]], to form the Mobile River.

After the completion of the Tennessee-Tombigee Waterway in [[1985]], much of the middle course of the river in northwestern Mississippi was diverted into the new straightened channel. Above Aberdeen Lake, the waterway flows alongside the original course of the river.

In addition to the Black Warrior, the river is joined by the [[Buttahatchee River]] from the east north of Columbus, Mississippi. Approximately 10 mi (16 km) north of Gainesville it is joined from the north by the [[Sipsey River]]. At Gainesville it is joined from the west by the [[Noxubee River]].

The [[Choctaw National Wildlife Refuge]] is along the river in southwestern Alabama, approximately 20 mi (32 km) northwest of Jackson.

==See also==
*[[List of Alabama rivers]]
*[[List of Mississippi rivers]]

==References==
*[[United States Geological Survey]] (2005). [http://geonames.usgs.gov/pls/gnis/web_query.GetDetail?tab=Y&id=692339 "Tombigbee River"]. Retrieved [[14 June]] [[2005]].

[[Category:Rivers of Alabama]]
[[Category:Rivers of Mississippi]]

The Foursquare Church

2006-02-02T23:23:12Z

RTC: /* Status */

[[Image:Angelus Temple.jpg|thumb|200px|The Angelus Temple, built by [[Aimee Semple McPherson]] and dedicated [[January 1]], [[1923]]. The temple is opposite Echo Park, near downtown [[Los Angeles, California]].]]The '''International Church of the Foursquare Gospel''' is an [[evangelical]] [[Pentecostal]] [[Christian]] denomination.

==Background==
[[Aimee Semple McPherson]] (1890-1944), a controversial female evangelist, founded the Foursquare Church in [[1927]]. Los Angeles was her center of operations, and the [[Angelus Temple]], seating 5,300 people, was opened there in [[1923]]. McPherson was an outright celebrity participating in publicity events such as parades every Sunday through the streets of L.A., along with the mayor and movie stars, directly to Angelus Temple. She built the temple, and [[L. I. F. E. Bible College]] next door to it, on the northwest corner of the land that she owned in the middle of the city.

Her son, Rolf K. McPherson, became president and leader of the church after her death in [[1944]]. Although he may not have had the same charisma his mother possessed, the denomination under his leadership grew from around 400 churches when his leadership began, to 10,000+ after his departure.

Together with the [[Assemblies of God]], the [[Church of God]], the [[Open Bible Standard Churches]], the [[International Pentecostal Holiness Church|Pentecostal Holiness Church]], and others, the Foursquare Church formed the "Pentecostal Fellowship of North America" in [[1948]] in [[Des Moines, Iowa]]. In [[1994]], it was reorganized as the [[Pentecostal/Charismatic Churches of North America]]. [[Jack W. Hayford]], founder of The Church on the Way in [[Van Nuys, California]], and Living Way Ministries, is perhaps the best-known foursquare minister in the [[21st century]] and is currently the denomination's President.

==Church doctrine==
The Foursquare Church believes in the following:
*The [[Bible]] as the inspired word of [[God]]
*The [[Trinity]]
*The atoning death of Christ for sinners
*Salvation through the grace of God by Faith Alone in the Lord Jesus Christ
*The necessity of repentance
*The new birth ([[Sanctification]])
*[[Baptism]] by immersion
*The memorial of [[The Lord's Supper]] as church ordinances
*The baptism of the [[Holy Spirit]]
*Divine healing
*The imminent return of Jesus Christ
*Final judgment

==Status==
As of [[2000]], the International Church of the Foursquare Gospel, commonly referred to as the Foursquare Church, had grown to 1844 churches with 218,981 members[[#Footnote|¹]] in the [[United States]]. Worldwide membership is over 3.5 million in almost 30,000 churches in 123 countries. Corporate headquarters are maintained in [[Los Angeles, California]]. In the United States, the church is divided into districts and local congregations affiliate with the district in their area. A General Supervisor oversees the national office and district supervisors. Glenn C. Burris, Jr., currently ([[2004]]) serves as General Supervisor. [[Jack W. Hayford]] has been the president of the International Church of the Foursquare Gospel since October 1, 2004. A number of educational institutions are affiliated with the Foursquare Church. Among these are [[Life Pacific College]], formerly "L. I. F. E. Bible College", in [[San Dimas, California]] and [[Pacific Life Bible College]] in [[Surrey, British Columbia]].

==External links==
*[http://www.foursquare.org/ International Church of the Foursquare Gospel] - official Web Site
*[http://www.lifecenter.net/ Life Center - Spokane, WA]
*[http://www.liferoads.org/ Life Roads, Spokane, WA]
*[http://www.lifecenternorth.org/ Life Center North - Spokane, WA]
*[http://www.eastpointchurch.org/ Eastpoint Church - Spokane Valley, WA]
*[http://www.epiclifechurch.org/ Epic Life Church - Spokane, WA]
*[http://www.livingway.org/ Living Way Ministries]
*[http://www.lifepacific.edu/ Life Pacific College - San Dimas]
*[http://www.pacificlife.edu/ Pacific Life Bible College - Surrey ]
*[http://www.kingscollege.edu/ The King's College and Seminary]
*[http://www.lifecenter.net/ Life Center - Spokane, WA]
*[http://www.EastBayFellowship.org/ EastBay Fellowship - Danville, CA]
*[http://www.livingwater.com/ Church of Living Water - Olympia, WA]
*[http://www.hopechristiancenterokc.org/ Hope Christian Center - Oklahoma City, OK]
*[http://www.oklahomafoursquare.org/ Oklahoma Foursquare District Website - Oklahoma City, OK]

==References==
*''Encyclopedia of American Religions'', J. Gordon Melton, editor
*''Handbook of Denominations in the United States'', by Frank S. Mead, Samuel S. Hill, and Craig D. Atwood
*''Religious Congregations & Membership in the United States (2000)'', Glenmary Research Center
*''The Vine and the Branches: A History of the International Church of the Foursquare Gospel'', by Nathaniel M. Van Cleave

==Footnote==
* 1. ''Religious Congregations & Membership in the United States (2000)''

[[category:Pentecostal denominations]]

Otis Young

2006-02-02T23:07:15Z

RTC:

'''Otis E. Young''' (born [[July 4]], [[1932]] in [[Providence, Rhode Island]]; died [[October 11]], [[2001]]) was an [[African-American]] actor. He was the first black actor to co-star in a [[televison]] [[Western (genre)|Western]], ''[[The Outcasts (TV series)|The Outcasts]]'' (1968-69). Young played another memorable role as [[Jack Nicholson]]'s shore-patrol partner in the [[1973]] comedy-drama film ''[[The Last Detail]]''.

Young, one of 14 children, joined the [[U.S. Marine Corps]] at the age of 17 and served in the [[Korean War]]. He then enrolled in acting classes at [[New York University]], trained at the [[Neighborhood Playhouse]], and worked off-Broadway as an actor and writer in the early 1960s. His first movie appearance was in ''[[Murder in Mississippi (1965 film)|Murder in Mississippi]]'' (1965).

In 1983 Young earned his bachelor's degree from [[L. I. F. E. Bible College]] in [[Los Angeles]] and became an ordained [[pastor]], eventually serving as senior pastor of Elim [[International Church of the Foursquare Gospel|Foursquare Gospel Church]] in [[Rochester, New York]] from 1986-1988. In 1989 he joined the faculty at [[Monroe Community College]] in Rochester; he remained there as a Professor of Communications and head of the Drama Department until his retirement in 1999.

Otis Young suffered a stroke in Los Angeles and died in [[2001]]. He was survived by his wife Barbara and four children.

==External links==
* {{imdb name|id=0949935|name=Otis Young}}

[[Category:1932 births|Young, Otis]]
[[Category:2001 deaths|Young, Otis]]
[[Category:American actors|Young, Otis]]

The Foursquare Church

2005-09-20T17:55:06Z

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[[Image:Angelus Temple.jpg|thumb|200px|The Angelus Temple, built by [[Aimee Semple McPherson]] and dedicated [[January 1]], [[1923]]. The temple is opposite Echo Park, near downtown [[Los Angeles, California]].]]The '''International Church of the Foursquare Gospel''' is a [[Pentecostal]] [[Christian]] denomination.

==Background==
[[Aimee Semple McPherson]] (1890-1944), a controversial female evangelist, founded the Foursquare Church in [[1927]]. Los Angeles was her center of operations, and the [[Angelus Temple]], seating 5,300 people, was opened there in [[1923]]. McPherson was an outright celebrity participating in publicity events such as parades every Sunday through the streets of L.A., along with the mayor and movie stars, directly to Angelus Temple. She built the temple, and [[L. I. F. E. Bible College]] next door to it, on the northwest corner of the land that she owned in the middle of the city.

Her son, Rolf K. McPherson, became president and leader of the church after her death in [[1944]]. Not being able to lead with the same charisma his mother possessed, the denomination became stagnant until a new generation of leaders emerged. Led by people like Chuck Smith, Jack Hayford, Roy Hicks, Jr., and Ralph Moore the Church began to convert the [[Hippie]] [[counterculture]] movement of the [[1960s]] and [[1970s|'70s]] to followers of their movement. The drug-drenched, spiritually voracious youth were converted in droves to the new paradigm churches that used guitars instead of organs, with bell-bottomed ministers preaching in a conversational tone of voice, rather than in an elocutionary one. The Jesus movement of the 1970s that gave the world "Jesus Rock" and a hip gospel to preach to the [[Woodstock Festival|Woodstock]] generation, was birthed by many of the graduates of the Bible College, by this time a citadel of Pentecostalism.

Together with the [[Assemblies of God]], the [[Church of God]], the [[Open Bible Standard Churches]], the [[International Pentecostal Holiness Church|Pentecostal Holiness Church]], and others, the Foursquare Church formed the "Pentecostal Fellowship of North America" in [[1948]] in [[Des Moines, Iowa]]. In [[1994]], it was reorganized as the [[Pentecostal/Charismatic Churches of North America]]. [[Jack W. Hayford]], founder of The Church on the Way in [[Van Nuys, California]], and Living Way Ministries, is perhaps the best-known foursquare minister in the [[21st century]] and is currently the denomination's President.

==The "Foursquare" Name==
The Foursquare (or four-fold) gospel is based on [[Jesus]] [[Christ]]'s four roles as Savior, Baptizer, Healer, and Coming King. The gospel exists for the body, soul, spirit, and eternity. McPherson revealed this idea at a revival in [[Oakland, California]], in [[1922]], after she claimed it came to her in a vision from God based on [[Ezekiel]]'s vision as recorded in Ezekiel chapter one. This is exemplified by the four faces representing Jesus Christ - the man (man of sorrows, Savior), the lion (baptizer with the Holy Ghost and fire), the ox (the Great Burden-bearer, Healer) and the eagle (the Coming King). Some claim that this idea did not originate with McPherson, but was rather only popularized by her.

==Church doctrine==
The Foursquare Church believes in the following:
*The [[Bible]] as the inspired word of [[God]]
*The [[Trinity]]
*The atoning death of Christ for sinners
*Salvation through the grace of God by Faith Alone in the Lord Jesus Christ
*The necessity of repentance
*The new birth ([[Sanctification]])
*[[Baptism]] by immersion
*The memorial of [[The Lord's Supper]] as church ordinances
*The baptism of the [[Holy Spirit]]
*Divine healing
*The imminent return of Jesus Christ
*Final judgment

==Status==
As of [[2000]], the International Church of the Foursquare Gospel had grown to 1844 churches with 218,981 members[[#Footnote|¹]] in the [[United States]]. Worldwide membership is over 3.5 million in almost 30,000 churches in 123 countries. Corporate headquarters are maintained in [[Los Angeles, California]]. In the United States, the church is divided into districts and local congregations affiliate with the district in their area. A General Supervisor oversees the national office and district supervisors. Glenn C. Burris, Jr., currently ([[2004]]) serves as General Supervisor. A number of educational institutions are affiliated with the Foursquare Church. Among these are [[Life Pacific College]], formerly Life Bible College, in [[San Dimas, California]] and [[Pacific Life Bible College]] in [[Surrey, British Columbia]].

==External links==
*[http://www.foursquare.org/ International Church of the Foursquare Gospel] - official Web Site
*[http://www.livingway.org/ Living Way Ministries]
*[http://www.lifepacific.edu/ Life Pacific College - San Dimas]
*[http://www.pacificlife.edu/ Pacific Life Bible College - Surrey ]
*[http://www.kingscollege.edu/ The King's College and Seminary]

==References==
*''Encyclopedia of American Religions'', J. Gordon Melton, editor
*''Handbook of Denominations in the United States'', by Frank S. Mead, Samuel S. Hill, and Craig D. Atwood
*''Religious Congregations & Membership in the United States (2000)'', Glenmary Research Center
*''The Vine and the Branches: A History of the International Church of the Foursquare Gospel'', by Nathaniel M. Van Cleave

==Footnote==
* 1. ''Religious Congregations & Membership in the United States (2000)''

[[category:Pentecostal denominations]]

IBM 729

2005-09-03T07:06:08Z

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[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|IBM 729s in action]]
The '''IBM 729 Magnetic Tape Unit''' was IBM's iconic [[magnetic tape|tape]] mass storage system from the late [[1950s]] through the mid [[1960s]]. It was used on [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used 1/2 [[inch]] (12.7 [[millimeter|mm]]) tape up to 2400 [[feet]] (730 [[meter]]s) long wound on reels up to 10-1/2 inch (267 mm) diameter. To allow rapid tape acceleration, long vacuum columns were placed between the tape reels and the [[tape head|read/write heads]]. The tape had seven parallel tracks, six for data and one to maintain odd [[parity]]. Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. [[Write protection]] was provided by a [[write protect ring|removable plastic ring]] in the back of the tape reel. A gap between records allowed the mechanism time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch. Later models supported 556 and 800 characters/inch.

==Reference:==
* IBM 709 Data Processing System, Form A22-6501-0

==External link==
*[http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)

[[Category:IBM hardware]]
[[Category:IBM_storage_devices]]

CDC 6600

2004-05-22T20:50:27Z

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The '''CDC 6600''' was a [[mainframe]] [[computer]] from [[Control Data Corporation]] built in 1965. It is generally considered to be the first successful [[supercomputer]] and completely outperformed all other machines in the world by a wide margin, typically 10 to 1.

It is generally agreed to have been the world's fastest computer from 1965 to 1969, when it was replaced by its own successor, the [[CDC 7600]]. The CDC 6600 was designed by [[Seymour Cray]] as soon as work had completed on the [[CDC 3600]], a much smaller computer. With sales of their other machines doing well, Control Data allowed Cray as much time as he liked to build his next design.

The basis for the 6600 is what we would today refer to as a [[RISC]] system, one in which the processor is tuned to do instructions which are comparatively simple. The philosophy of many other machines was toward using instructions which were complicated — for example, which would fetch an operand from memory and add it to a value in a register. In the 6600, loading the value from memory would require one instruction, and adding it would require a second.

To handle the 'household' tasks which other designs put in the CPU, Cray included in the 6600 ten other processors, based partly on his earlier computer, the [[CDC 160A]]. These machines, called peripheral processors, or PPUs, were full computers in their own right, but tuned to performing [[Input/output|I/O]] tasks and running the operating system. When the main CPU needed to perform some sort of I/O, it instead loaded a small program into one of these other machines.

The central processor had 60-bit words, while the peripheral processors had 12-bit words (like the later DEC [[PDP-8]] minicomputer). Characters/'bytes' were 6-bit, and central processor instructions were either 15 bits, or 30 bits with an 18-bit address field, the latter allowing for a directly addressable memory space of 256 K words (converted to modern terms, with 8-bit bytes, this is the same amount of bits as in a memory of 1.88 megabytes).

===External Links===
*[http://research.microsoft.com/users/gbell/craytalk/sld001.htm Presentation of the CDC 6600 and other machines designed by Seymour Cray] – by C. [[Gordon Bell]] of Microsoft Research (formerly of DEC)

Crosley Motors

2004-04-17T07:22:47Z

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The '''Crosley''' was an [[automobile]] manufactured by Crosley Motors Incorporated from May, [[1939]] to [[1952]] when the factory was sold to General Tire and Rubber.

==External links==
*[http://www.geocities.com/motorcity/garage/7896/crosley.htm CROSLEY A Compact born 30 years too soon!]
*[http://www.ggw.org/~cac/ Crosley Automobile Club Inc.]

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CDC 6600

2004-04-11T03:42:49Z

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The '''CDC 6600''' was a [[mainframe]] [[computer]] from [[Control Data Corporation]] built in 1965. It is generally considered to be the first successful [[supercomputer]] and completely outperformed all other machines in the world by a wide margin, typically 10 to 1. It is generally agreed to have been the world's fastest computer from 1965 to 1969, when it was replaced by its own successor, the [[CDC 7600]].

The CDC 6600 was designed by [[Seymour Cray]] as soon as work had completed on the [[CDC 3600]], a much smaller computer. With sales of their other machines doing well, CDC allowed Cray as much time as he liked to build his next design.

The basis for the 6600 is what we would today refer to as a [[RISC]] system, one in which the processor is tuned to do instructions which are comparatively simple. The philosophy of many other machines was toward using instructions which were complicated — for example, which would fetch an operand from memory and add it to a value in a register. In the 6600, loading the value from memory would require one instruction, and adding it would require a second.

To handle the "day to day" tasks which other designs put in the CPU, Cray included in the 6600 10 copies of another kind of processor, based in many ways on his earlier computer, the 160A. These machines, called peripheral processors, or PPUs, were full computers in their own right, but tuned to performing [[Input/output|I/O]] tasks, and running the operating system. When the main CPU needed to perform some sort of I/O, it instead sent (or loaded) a small program into one of these other machines.

The central processor had 60-bit words, and the peripheral processors had 12-bit words. Characters were 6-bit, and central processor instructions were 15 bits or 30 bits, with an 18 bit address field.

===External Links===

*Presentation by [[Gordon Bell]] of [[Microsoft]] about the CDC6600 and other [[Cray]] machines, [http://research.microsoft.com/users/gbell/craytalk/sld001.htm here].