The first Prolog was written in Algol-W. The second one, which was called Prolog I was written in Fortran. See comments for more: https://stackoverflow.com/a/44

The first Prolog was written in Algol-W. The second one, which was called Prolog I was written in Fortran. See comments for more: https://stackoverflow.com/a/4478969 https://stackoverflow.com/a/4478969