ABC (programming)

ABC is an imperative language and programming environment from CWI, Netherlands. It is interactive, structured, high-level, and easy to learn and use. It is a general-purpose language which you might use instead of BASIC, Pascal, or AWK. It is not a systems-programming language but is good for teaching or prototyping.

ABC has only five data types that can easily be combined; strong typing, yet without declarations; data limited only by memory; refinements to support top-down programming; nesting by indentation. Programs are typically around a quarter the size of the equivalent Pascal or C program, and more readable.

ABC includes a programming environment with syntax-directed editing, suggestions, persistent variables and multiple workspaces and infinite precision arithmetic.

An example function words to collect the set of all words in a document:

  HOW TO RETURN words document:
     PUT {} IN collection
     FOR line in document:
        FOR word IN split line:
           IF word not.in collection:
              INSERT word IN collection
     RETURN collection

Interpreter/compiler, version 1.04.01, by Leo Geurts, Lambert Meertens, Steven Pemberton <Steven.Pemberton@cwi.nl>. ABC has been ported to Unix, MS-DOS, Atari, Macintosh.