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, Occam
William of. died ?1349, English nominalist philosopher, who contested the temporal power of the papacy and ended the conflict between nominalism and realism


(Note lower case) A language based on Anthony Hoare's CSP and David May's EPL. Named after the English philosopher, William of Occam (1300-1349) who propounded Occam's Razor. The occam language was designed by David May of INMOS to easily describe concurrent processes which communicate via one-way channels. It was developed to run on the INMOS transputer but compilers are available for VAX, Sun and Intel MDS, inter alia.

The basic entity in occam is the process of which there are four fundamental types, assignment, input, output, and wait. More complex processes are constructed from these using SEQ to specify sequential execution, PAR to specify parallel execution and ALT where each process is associated with an input from a channel. The process whose channel inputs first is executed. The fourth constructor is IF with a list of conditions and associated processes. The process executed is the one with the first true condition in textual order. There is no operator precedence.

The original occam is now known as "occam 1". It was extended to occam 2.

Simulator for VAX.

Tahoe mailing list: <occam@sutcase.case.syr.edu>.

[David May et al, 1982. "Concurrent algorithms"].

["Occam", D. May, SIGPLAN Notices 18(4):69-79, 1983].


An early parallel processing language from Inmos Limited that was developed in the 1980s to handle concurrent operations. The Inmos Transputer executed occam almost directly. In the following statements, two items of data are read and incremented at the same time. PAR specifies that following statements are to be executed concurrently, and SEQ indicates that the following statements are executed sequentially. See transputer.

PARSEQchan1 ? item1item1 := item1 + 1SEQchan2 ? item2item2 := item2 + 1
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