B is a programming language developed at Bell Labs circa 1969. It is the work of Ken Thompson
with Dennis Ritchie. B first appeared circa 1969.
B was derived from BCPL, and its name may be a contraction of BCPL. It is possible that
its name may be based on Bon, an earlier but unrelated, and rather different, programming
language that Thompson designed for use on Multics.
B was designed for recursive, non-numeric, machine independent applications, such as
system and language software.
History Initially Ken Thompson and later Dennis Ritchie
developed B basing it mainly on the BCPL language Thompson used in the Multics project. B was
essentially the BCPL system stripped of any component Thompson felt he could do without
in order to make it fit within the memory capacity of the minicomputers of the time.
The BCPL to B transition also included changes made to suit Thompson's preferences. Much
of the typical algol-like syntax of BCPL was rather heavily changed in this process, such
as the := and = operators which were replaced with = for assignment and == for equality
test. Thomson invented arithmetic assignment operators
for B, using x=+y to add y to x. B also introduced the increment and decrement operators; Their
prefix or postfix position determines whether the value is taken prior or post alteration
of the operand. These innovations were not in the earliest versions of B. Some guess
that they were created for the auto-increment and auto-decrement address modes of the DEC
PDP-11. This is historically impossible as there was no PDP-11 at the time that B was
developed. B is typeless, or more precisely has one data
type: the computer word. Most operators treated this as an integer, but others treated it
as a memory address to be dereferenced. In many other ways it looked a lot like an early
version of C. There are a few library functions, including some that vaguely resemble functions
from the standard I/O library in C. Early implementations were for the DEC PDP-7
and PDP-11 minicomputers using early Unix, and Honeywell GE 645 36-bit mainframes running
the operating system GCOS. The earliest PDP-7 implementations compiled to threaded code,
and then Ritchie wrote a compiler using TMG which produced machine code. In 1970 a PDP-11
was acquired and threaded code was used for the port. An early version of yacc was produced
with this PDP-11 configuration. Ritchie took over maintenance during this period.
The typeless nature of B made sense on the Honeywell, PDP-7 and many older computers,
but was a problem on the PDP-11 because it was difficult to elegantly access the character
data type that the PDP-11 and most modern computers fully support. Starting in 1971
Ritchie made changes to the language while converting its compiler to produce machine
code, most notably adding data typing for variables. During 1971 and 1972 B evolved
into "New B" and then C. B continues to see use on GCOS mainframes,
and on certain embedded systems for a variety of reasons, including limited hardware in
the small systems; extensive libraries, tools, licensing cost issues; and simply being good
enough for the job on others. The highly influential AberMUD was originally written in B.
B is almost extinct, having been superseded by the C language.
Examples The following example is from the Users' Reference
to B by Ken Thompson:
See also References
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. 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.