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COWSEL (COntrolled Working SpacE Language) is a programming language designed between 1964 and 1966 by Robin Popplestone. It was based on a reverse Polish notation (RPN) form of the language Lisp, combined with some ideas from Combined Programming Language (CPL).

COWSEL was initially implemented on a Ferranti Pegasus computer at the University of Leeds and on a Stantec Zebra at the Bradford Institute of Technology. Later, Rod Burstall implemented it on an Elliot 4120 at the University of Edinburgh.

COWSEL was renamed POP-1 in 1966, during summer, and development continued under that name from then on.

Example code

function member
lambda x y
comment Is x a member of list y;
define      y atom then *0 end
            y hd x equal then *1 end
            y tl -> y repeat up

Reserved words (keywords) were also underlined in the original printouts. Popplestone performed syntax highlighting by using underscoring on a Friden Flexowriter.

See also

  • POP-2 programming language
  • POP-11 programming language
  • Poplog programming environment

References

  • Technical report: EPU-R-12, U Edinburgh (Apr 1966)