18-bit computing
 | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (October 2009) |
| Computer architecture bit widths |
|---|
| Bit |
| Application |
| Binary floating-point precision |
| Decimal floating-point precision |
In computer architecture, 18-bit integers, memory addresses, or other data units are those that are 18 bits (2.25 octets) wide. Also, 18-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size.
18 binary digits have 262144 (1000000 octal, 40000 hexadecimal) distinct combinations.
18 bits was a common word size for smaller computers in the 1960s, when large computers often used 36 bit words and 6-bit character sets were the norm.
Example 18-bit computer architectures
- Possibly the most well-known 18-bit computer architectures are the PDP-1, PDP-4, PDP-7, PDP-9 and PDP-15 minicomputers produced by Digital Equipment Corporation from 1960 to 1975.
- UNIVAC produced a number of 18-bit computers, including the UNIVAC 418 and several military systems.
- The IBM 7700 Data Acquisition System was an 18-bit computer.
- The BCL Molecular
- The NASA Standard Spacecraft Computer NSSC-1