ABC was Python's most direct predecessor; I worked on it from around 1983-1986.

I downloaded these sources from cwi.nl, specifically the abc-unix tarball.

Another copy of the ABC sources lives in Luciano Ramalho's GitHub. I hope one day to compare the two trees and unify them.

Most files have 1991 as their latest modification time in the tar ball; a few have 1996 or 2021.

The old README file has build instructions.

The current sources assume a 32-bit system where int and pointers have the same size. I hope to eventually upgrade the source code to work on 64-bit systems too (where int is 32 bits and pointers are 64 bits).

CWI never put a license on ABC, but it says:

Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1988-2011.

I'll try to negotiate with Steven Pemberton eventually (hopefully MIT).

Eddy Boeve, Frank van Dijk, Leo Geurts, Timo Krijnen, Lambert Meertens, Steven Pemberton, Guido van Rossum.

• Leo Geurts, Lambert Meertens and Steven Pemberton, The ABC Programmer's Handbook, Prentice-Hall, Englewood Cliffs, New Jersey, 1990, ISBN 0-13- 000027-2.
• Steven Pemberton, An Alternative Simple Language and Environment for PCs, IEEE Software, Vol. 4, No. 1, January 1987, pp. 56-64. http://www,cwi.nl/~steven/abc.html