B (programming language)
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B is a
programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...
developed at
Bell Labs Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, Murray Hill, New Jersey, the compa ...
circa 1969 by
Ken Thompson Kenneth Lane Thompson (born February 4, 1943) is an American pioneer of computer science. Thompson worked at Bell Labs for most of his career where he designed and implemented the original Unix operating system. He also invented the B (programmi ...
and
Dennis Ritchie Dennis MacAlistair Ritchie (September 9, 1941 – October 12, 2011) was an American computer scientist. He created the C programming language and the Unix operating system and B language with long-time colleague Ken Thompson. Ritchie and Thomp ...
. B was derived from
BCPL BCPL ("Basic Combined Programming Language") is a procedural, imperative, and structured programming language. Originally intended for writing compilers for other languages, BCPL is no longer in common use. However, its influence is still f ...
, 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 Multics ("MULTiplexed Information and Computing Service") is an influential early time-sharing operating system based on the concept of a single-level memory.Dennis M. Ritchie, "The Evolution of the Unix Time-sharing System", Communications of t ...
. B was designed for recursive, non-numeric, machine-independent applications, such as system and language software. 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 An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...
or a
memory address In computing, a memory address is a reference to a specific memory location in memory used by both software and hardware. These addresses are fixed-length sequences of digits, typically displayed and handled as unsigned integers. This numeric ...
. As machines with
ASCII ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...
processing became common, notably the DEC PDP-11 that arrived at Bell Labs, 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 ubiquitous
C programming language C (''pronounced'' '' – like the letter c'') is a general-purpose programming language. It was created in the 1970s by Dennis Ritchie and remains very widely used and influential. By design, C's features cleanly reflect the capabilities of ...
.


History

Circa 1969,
Ken Thompson Kenneth Lane Thompson (born February 4, 1943) is an American pioneer of computer science. Thompson worked at Bell Labs for most of his career where he designed and implemented the original Unix operating system. He also invented the B (programmi ...
and later Dennis Ritchie developed B basing it mainly on the
BCPL BCPL ("Basic Combined Programming Language") is a procedural, imperative, and structured programming language. Originally intended for writing compilers for other languages, BCPL is no longer in common use. However, its influence is still f ...
language Thompson used in the
Multics Multics ("MULTiplexed Information and Computing Service") is an influential early time-sharing operating system based on the concept of a single-level memory.Dennis M. Ritchie, "The Evolution of the Unix Time-sharing System", Communications of t ...
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 (mostly along the lines of reducing the number of non-whitespace characters in a typical program). Much of the typical
ALGOL ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the ...
-like syntax of BCPL was rather heavily changed in this process. The assignment operator := reverted to the = of Rutishauser's Superplan, and the equality operator = was replaced by

. Thompson added "two-address assignment operators" using x =+ y syntax to add y to x (in C the operator is written +=). This syntax came from
Douglas McIlroy Malcolm Douglas McIlroy (born 1932) is an American mathematician, engineer, and programmer. As of 2019 he is an Adjunct Professor of Computer Science at Dartmouth College. McIlroy is best known for having originally proposed Unix pipelines and de ...
's implementation of TMG, in which B's compiler was first implemented (and it came to TMG from
ALGOL 68 ALGOL 68 (short for ''Algorithmic Language 1968'') is an imperative programming language member of the ALGOL family that was conceived as a successor to the ALGOL 60 language, designed with the goal of a much wider scope of application and ...
's x +:= y syntax). Thompson went further by inventing the increment and decrement operators (++ and --). Their prefix or postfix position determines whether the value is taken before or after alteration of the operand. This innovation was not in the earliest versions of B. According to Dennis Ritchie, people often assumed that they were created for the auto-increment and auto-decrement address modes of the DEC PDP-11, but this is historically impossible as the machine didn't exist when B was first developed. The semicolon version of the
for loop In computer science, a for-loop or for loop is a control flow Statement (computer science), statement for specifying iteration. Specifically, a for-loop functions by running a section of code repeatedly until a certain condition has been satisfi ...
was borrowed by Ken Thompson from the work of Stephen Johnson. B is typeless, or more precisely has one data type: the computer word. Most operators (e.g. +, -, *, /) 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. In Thompson's words: "B and the old old C were very very similar languages except for all the types n C. Early implementations were for the DEC
PDP-7 The PDP-7 is an 18-bit computing, 18-bit minicomputer produced by Digital Equipment Corporation as part of the Programmed Data Processor, PDP series. Introduced in 1964, shipped since 1965, it was the first to use their Flip-Chip module, Flip- ...
and
PDP-11 The PDP–11 is a series of 16-bit minicomputers originally sold by Digital Equipment Corporation (DEC) from 1970 into the late 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of a ...
minicomputers using early
Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
, and
Honeywell Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...
36-bit mainframes running the operating system GCOS. The earliest PDP-7 implementations compiled to threaded code, and 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 assembler, , and the B language itself were written in B to bootstrap the computer. An early version of
yacc Yacc (Yet Another Compiler-Compiler) is a computer program for the Unix operating system developed by Stephen C. Johnson. It is a lookahead left-to-right rightmost derivation (LALR) parser generator, generating a LALR parser (the part of a co ...
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" (NB) and then C. B is almost extinct, having been superseded by the
C language C (''pronounced'' '' – like the letter c'') is a general-purpose programming language. It was created in the 1970s by Dennis Ritchie and remains very widely used and influential. By design, C's features cleanly reflect the capabilities o ...
. However, it continues to see use on GCOS mainframes () and on certain
embedded systems An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is em ...
() for a variety of reasons: limited hardware in small systems, extensive libraries, tooling, licensing cost issues, and simply being good enough for the job. The highly influential AberMUD was originally written in B.


Examples

The following examples are from the ''Users' Reference to B'' by Ken Thompson: /* 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) /* 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 conver- sion of the expansion 1/2! + 1/3! + ... = .111... where the bases of the digits are 2, 3, 4, ... */ main() v
000 Triple zero, Zero Zero Zero, 0-0-0 or variants may refer to: * 000 (emergency telephone number), the Australian emergency telephone number * 000, the size of several small List of screw drives, screw drives * 0-0-0, a Droid (Star Wars)#0-0-0, dro ...
n 2000;


Notes


References


External links


Manual page for b(1) from Unix First Edition


Dennis M. Ritchie. Puts B in the context of
BCPL BCPL ("Basic Combined Programming Language") is a procedural, imperative, and structured programming language. Originally intended for writing compilers for other languages, BCPL is no longer in common use. However, its influence is still f ...
and C. *
Users' Reference to B
', Ken Thompson. Describes the
PDP-11 The PDP–11 is a series of 16-bit minicomputers originally sold by Digital Equipment Corporation (DEC) from 1970 into the late 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of a ...
version.
The Programming Language B
S. C. Johnson & B. W. Kernighan, Technical Report CS TR 8,
Bell Labs Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, Murray Hill, New Jersey, the compa ...
(January 1973). The GCOS version on
Honeywell Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...
equipment.
B Language Reference Manual
Thinkage Ltd. The production version of the language as used on GCOS, including language and runtime library. {{portalbar, Computer programming Procedural programming languages Programming languages Programming languages created in 1969