B (programming language)
| B | |
|---|---|
| Designed by | Ken Thompson |
| Developer | Ken Thompson, Dennis Ritchie |
| First appeared | 1969[1] |
| Typing discipline | typeless (everything is a word) |
| Filename extensions | .b |
| Influenced by | |
| BCPL, PL/I, TMG | |
| Influenced | |
| C | |
B is a programming language developed at Bell Labs circa 1969 by Ken Thompson and Dennis Ritchie.
B was derived from BCPL, and its name may possibly be a contraction of BCPL. Thompson's coworker Dennis Ritchie speculated that the name might be based on Bon, an earlier, but unrelated, programming language that Thompson designed for use on Multics.[note 1]
B was designed for recursive, non-numeric, machine-independent applications, such as system and language software.[3] It was a typeless language, with the only data type being the underlying machine's natural memory word format, whatever that might be. Depending on the context, the word was treated either as an integer or a memory address.
As machines with ASCII processing became common, notably the DEC PDP-11 that arrived at Bell, support for character data stuffed in memory words became important. The typeless nature of the language was seen as a disadvantage, which led Thompson and Ritchie to develop an expanded version of the language supporting new internal and user-defined types, which became the C programming language.
Examples
The following examples are from the Users' Reference to B by Ken Thompson:[3]
/* The following function will print a non-negative number, n, to
the base b, where 2<=b<=10. This routine uses the fact that
in the ASCII character set, the digits 0 to 9 have sequential
code values. */
printn(n, b) {
extrn putchar;
auto a;
/* Wikipedia note: the auto keyword declares a variable with
automatic storage (lifetime is function scope), not
"automatic typing" as in C++11. */
if (a = n / b) /* assignment, not test for equality */
printn(a, b); /* recursive */
putchar(n % b + '0');
}
/* The following program will calculate the constant e-2 to about
4000 decimal digits, and print it 50 characters to the line in
groups of 5 characters. The method is simple output conversion
of the expansion
1/2! + 1/3! + ... = .111....
where the bases of the digits are 2, 3, 4, . . . */
main() {
extrn putchar, n, v;
auto i, c, col, a;
i = col = 0;
while(i<n)
v[i++] = 1;
while(col<2*n) {
a = n+1;
c = i = 0;
while (i<n) {
c =+ v[i] *10;
v[i++] = c%a;
c =/ a--;
}
putchar(c+'0');
if(!(++col%5))
putchar(col%50?' ': '*n');
}
putchar('*n*n');
}
v[2000];
n 2000;
See also
Notes
- ^ "Its name most probably represents a contraction of BCPL, though an alternate theory holds that it derives from Bon [Thompson 69], an unrelated language created by Thompson during the Multics days. Bon in turn was named either after his wife Bonnie or (according to an encyclopedia quotation in its manual), after a religion whose rituals involve the murmuring of magic formulas."[2]
References
- ^ "B - computer programming language".
- ^ Ritchie, Dennis M. (March 1993). "The Development of the C Language". ACM SIGPLAN Notices. 28 (3): 201–208. doi:10.1145/155360.155580.
- ^ a b Thompson, Ken (7 January 1972). "Users' Reference to B" (PDF). Bell Laboratories. Archived from the original (PDF) on 17 March 2015. Retrieved 21 March 2014.
External links
- Manual page for b(1) from Unix First Edition
- The Development of the C Language, Dennis M. Ritchie. Puts B in the context of BCPL and C.
- Users' Reference to B, Ken Thompson. Describes the PDP-11 version.
- The Programming Language B, S. C. Johnson & B. W. Kernighan, Technical Report CS TR 8, Bell Labs (January 1973). The GCOS version on Honeywell equipment.
- B Language Reference Manual, Thinkage Ltd. The production version of the language as used on GCOS, including language and runtime library.
