Occam (programming language): Difference between revisions

Revision as of 00:01, 13 December 2005

Revision as of 11:42, 18 December 2005

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:''Do not confuse it with the [[Ocaml]] language.''

'''Occam''' (officially written in lowercase as '''occam''') is a [[Parallel computing|parallel]] [[programming language]] that builds on [[Communicating Sequential Processes]] (CSP) and shares many of their features. It is named after [[William of Ockham]] of [[Occam's Razor]] fame. Occam is, in a way, a practical executable implementation of CSP.

Occam is an [[imperative (programming)|imperative]] [[procedural (programming)|procedural]] language (such as [[Pascal (programming language)|Pascal]]). It was developed by [[InmosINMOS]] as the native programming language for their line of [[Transputertransputer]] [[microprocessor]]s, but implementations for other platforms exist as well.

==Overview==

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==Language revisions==

===Occamoccam 21===

'''Occam 1''' was a preliminary version of the language. This supported only the VAR data type, which was an integral type corresponding to the native word length of the target architecture, and one-dimensional arrays.

'''Occam 2''' is an extension produced by INMOS Ltd in 1987 that adds floating-point, functions and more language types like varying sizes of integers (INT16, INT32) and character types.

===occam 2===

With this revision Occam became a language capable of expressing useful programs, whereas occam 1 was more suited to examining algorithms and exploring the new language.

'''Occam 2''' is an extension produced by INMOS Ltd in 1987 that adds [[floating-point]] support, functions, multi-dimensional arrays and more languagedata types likesuch as varying sizes of integers (INT16, INT32) and character typesbytes.

With this revision, Occamoccam became a language capable of expressing useful programs, whereas occam 1 was more suited to examining algorithms and exploring the new language.

["occam 2 Reference Manual", [[INMOS]], P-H 1988, ISBN 0-13-629312-3].

===Occamoccam 2.1===

'''Occam 2.1''' is a second enhancement to occam, produced in 1988 by [[INMOS]] Ltd. It was the last of the series language developments contributed by INMOS. Despite its "incremental" version number, it was a significant upgrade in the usefulness of the language, introducing:

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* Ability to return fixed-length array from function;

For a full list of the changes see Appendix P of the [http://www.wotug.org/occam/documentation/oc21refman.pdf INMOS Occamoccam 2.1 Reference Manual].

===Occamoccam 3===

'''Occam 3''' was the name for a proposal for the next-generation occam language, created by one of the senior programmers at INMOS. A specification was created and distributed for community comment. The new language included a large number of changes, many of which were focussed at making code sharing, simultaneous development, and project reuse easier.

The [http://www.wotug.org/occam/documentation/oc3refman.pdf Occamoccam 3] specification is available, but no compiler was created for this variant of the language, partly due to problems within [[INMOS]] and its subsequent takeover.

Some elements from occam 3 were introduced into the occam 2.1 compiler by other teams, and came to be known as 'occam 2.5' - as in "half-way there"!

===Occamoccam 2.5===

'''Occam 2.5''' is the common name for the language compiled by the Kent Retargettable Occamoccam compilerCompiler [[KRoC]]. It contains a significant number of extensions to the occam 2.1 compiler, for example:

* nested protocols

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* extended rendezvous.

The KRoC team have made the compiler available on their website. In recent times, the team has decided to rename the compiler to [[Occamoccam-Pipi]], because of the use of theories from the [[Pi-calculus]].

==External links==