BCPL (Basic Combined Programming Language) is a computer programming language that was designed by Martin Richards of the University of Cambridge in 1966; it was originally intended for use in writing compilers for other languages. Although not widely used now, it was very influential, because Dennis Ritchie would later develop the widely-used C programming language from BCPL. The tower of a personal computer (specifically a Power Mac G5). ... A programming language or computer language is a standardized communication technique for expressing instructions to a computer. ... Martin Richards is a British computer scientist, best known for his development of the BCPL programming language, which is both the earliest major development in portable software, and the ancestor of the widely used C programming language. ... The University of Cambridge is the second-oldest university in the English-speaking world. ... 1966 was a common year starting on Saturday (the link is to a full 1966 calendar). ... A diagram of the operation of an ideal compiler. ... Ken Thompson (left) with Dennis Ritchie (right) Dennis MacAlistair Ritchie (September 9, 1941- ) is a computer scientist notable for his influence on ALTRAN, B, BCPL, C, Multics, and UNIX. Born in Bronxville, New York, Ritchie graduated from Harvard with degrees in physics and applied mathematics. ... The C Programming Language, Brian Kernighan and Dennis Ritchie, the original edition that served for many years as an informal specification of the language The C programming language is a standardized programming language developed in the early 1970s by Ken Thompson and Dennis Ritchie for use on the UNIX operating...

BCPL was a response to difficulties with its predecessor CPL, created during the early 1960s; Richards created BCPL by "removing those features of the full language which make compilation difficult". The first compiler implementation, for the IBM 7094 under CTSS, was written while Richards was visiting Project MAC at MIT in the spring of 1967. The language was first described in a paper presented to the 1969 Spring Joint Computer Conference. The Combined Programming Language (CPL) was a computer programming language developed jointly between the Mathematical Laboratory at the University of Cambridge and the University of London Computer Unit during the 1960s. ... Events and trends The 1960s was a turbulent decade of change around the world. ... The IBM 7094 the fourth member of the most popular family of IBMs large second-generation transistorized mainframe computers and was designed for large-scale scientific and technological applications. The first 7094 installation was in September 1962. ... This article is about the MIT Project MAC operating system. ... Project MAC, later the MIT Laboratory for Computer Science (LCS), was a research laboratory at MIT. Project MAC would become famous for groundbreaking research in operating systems, artificial intelligence, and the theory of computation. ... The Massachusetts Institute of Technology, or MIT, is a research institution and university located in the city of Cambridge, Massachusetts directly across the Charles River from Bostons Back Bay district. ... 1967 was a common year starting on Sunday of the Gregorian calendar. ...

The language is clean, powerful, and portable. It therefore proved possible to write small and simple compilers for it; reputedly some compilers could be run in 16 kilobytes. In addition, the Richards compiler, itself written in BCPL, was easily portable. BCPL was therefore a popular choice for bootstrapping a system. A kilobyte (derived from the SI prefix kilo-) is a unit of information or computer storage equal to one thousand bytes. ... Bootstrapping alludes to a German legend about a Baron Münchhausen, who was able to lift himself out of a swamp by pulling himself up by his own hair. ...

A major reason for the compiler's portability lay in its structure. It was split into two parts: the front end parsed the source and generated O-code for a virtual machine, and the backend took the O-code and translated it into the code for the target machine. Only 1/5th of the compiler's code needed to be rewritten to support a new machine, a task that usually took between 2 and 5 man-months. Soon afterwards this structure became fairly common practice, cf. Pascal or Java, but the Richards BCPL compiler was the first to define a virtual machine for this purpose. The O-code machine is a virtual machine that was developed by Martin Richards in the late 1960s to give machine independence to BCPL, the low-level forerunner to C and C++. The concept behind the O-Code machine was to create O-code output (O stands for Object) through... In general terms, a virtual machine in computer science is software that creates an environment between the computer platform and the end user in which the end user can operate software. ... Pascal is one of the landmark computer programming languages on which generations of students cut their teeth and variants of which are still widely used today. ... Java is an object-oriented programming language developed initially by James Gosling and colleagues at Sun Microsystems. ...

The language is unusual in having only one data type: a word, a fixed number of bits, usually chosen to align with the architecture's machine word. This choice later proved to be a significant problem when BCPL was used on machines in which the smallest addressable item was not a word, but a byte. On computer science, a datatype (often simply type) is a name or label for a set of values and some operations which can be performed on that set of values. ... Word can mean one of several things: A linguistic word—a unit of language that symbolizes or communicates a meaning, consisting of one or more morphemes. ... This article refers to the unit of binary information. ...

The interpretation of any value was determined by the operators used to process the values. (For example, + added two values together treating them as integers; ! indirected through a value, effectively treating it as a pointer.) In order for this to work, the implementation provided no type checking. The Hungarian Notation was developed to help programmers avoid inadvertent type errors. The integers consist of the positive natural numbers (1, 2, 3, …) the negative natural numbers (−1, −2, −3, ...) and the number zero. ... On computer science, a datatype (often simply type) is a name or label for a set of values and some operations which can be performed on that set of values. ... Hungarian notation is a naming convention in computer programming, in which the name of an object indicates its type and intended use. ...

It is reputedly the language in which the original hello world program was written. The first MUD was also written in BCPL [1] (http://www.mudconnect.com/mud_intro.html). A hello world program is a computer program that prints out Hello, world! on a display device. ... In computer gaming, a MUD (multi-user dungeon, dimension, or sometimes domain) is a multi-player computer game that combines elements of role-playing games, hack-and-slash style computer games, and social Internet Relay Chat channels. ...

Several operating systems were written partially or wholly in BCPL (for example, TRIPOS or Amiga Kickstart). BCPL was also the initial language used in the seminal Xerox PARC Alto project, the first modern personal computer; among many other influential projects, the ground-breaking Bravo document preparation system was written in BCPL. The University of Cambridge, Cambridge, England, divides the different kinds of honours bachelors degree by Tripos, a word which has an obscure etymology, but which may be traced to the three-legged stool candidates once used to sit on when taking oral examinations. ... AmigaOS is the default native operating system of the Amiga and AmigaOne personal computers. ... Xerox Palo Alto Research Center (PARC) was a flagship research division of the Xerox Corporation, based in Palo Alto, California, USA. It was founded in 1970 and spun out as a separate company in 2002. ... The Xerox Alto, developed at Xerox PARC in 1973, was the first personal computer and the first computer to use the desktop metaphor and graphical user interface (GUI). ... Bravo was the first WYSIWYG document preparation program. ... A word processor (also more formally known as a document preparation system) is a computer application used for the production (including composition, editing, formatting, and possibly printing) of any sort of viewable or printed material. ...

By 1970, implementations existed for the Honeywell 635 and 645, the IBM 360, the TX-2, the CDC 6400, the Univac 1108, the PDP-9, the KDF 9 and the Atlas 2. In 1979 implementations existed for at least 25 architectures; in 2001 it sees little use. The IBM System/360 (S/360) is a computer system family announced by International Business Machines on April 7, 1964. ... The MIT Lincoln Laboratory TX-2 computer was the successor to the Lincoln TX-0 and was known for its role in advancing both artificial intelligence and human-computer interaction. ... The CDC 6400 was a mainframe computer made my Control Data Corporation in the 1960s. ... PDP is also used as an acronym for Plasma Display Panel. ...

The philosophy of BCPL can be summarised by quoting from the book BCPL, the language and its compiler:

The philosophy of BCPL is not one of the tyrant who thinks he knows best and lays down the law on what is and what is not allowed; rather, BCPL acts more as a servant offering his services to the best of his ability without complaint, even when confronted with apparent nonsense. The programmer is always assumed to know what he is doing and is not hemmed in by petty restrictions.

The design, and philosophy, of BCPL strongly influenced B, which in turn influenced C. C is now the language of choice for systems programming. B was the name of a programming language developed at Bell Labs. ... The C Programming Language, Brian Kernighan and Dennis Ritchie, the original edition that served for many years as an informal specification of the language The C programming language is a standardized programming language developed in the early 1970s by Ken Thompson and Dennis Ritchie for use on the UNIX operating... System programming (or systems programming) is the activity of building and maintaining, low-level, system software for computers, including operating systems, system utilities, compilers, and so forth. ...

Sources

• Martin Richards, The BCPL Reference Manual (http://cm.bell-labs.com/cm/cs/who/dmr/bcpl.html) (Memorandum M-352, Project MAC, Cambridge, July, 1967)
• Martin Richards, BCPL - a tool for compiler writing and systems programming (Proceedings of the Spring Joint Computer Conference, Vol 34, pp 557-566, 1969)
• Martin Richards, Arthur Evans, Robert F. Mabee, The BCPL Reference Manual (MAC TR-141, Project MAC, Cambridge, 1974)
• Martin Richards, C. Whitby-Strevens, BCPL, the language and its compiler (Cambridge University Press, 1980) ISBN 0-521-28681-6

External links

• Martin Richards' BCPL distribution (http://www.cl.cam.ac.uk/users/mr/BCPL.html)
• Martin Richards's BCPL Reference Manual (http://cm.bell-labs.com/cm/cs/who/dmr/bcpl.html) by Dennis M. Ritchie also includes some fascinating commentary from him about BCPL's influence on C
• BCPL entry (http://www.catb.org/~esr/jargon/html/B/BCPL.html) in the Jargon File