Prolog, short for PROgrammation en LOGique, was created by Alain Colmerauer and Philippe Roussel at the University of Aix-Marseille around 1972. A preliminary version came together at the end of 1971 and a more definitive one at the end of 1972, growing out of a project to process natural language, specifically French. Roussel chose the name. The two researchers told this story themselves in their paper “The birth of Prolog,” delivered at the ACM conference on the History of Programming Languages, which is the primary source cited here.
Prolog was a radical departure from languages like Fortran or Lisp. Instead of telling the computer step by step how to compute something, a Prolog programmer states facts and rules in a logical form and then asks questions; the system searches for answers on its own. The execution engine underneath is a restricted, efficient form of the resolution principle that John Alan Robinson had introduced in 1965, applied to a class of statements called Horn clauses. The theoretical case that logic itself could be used as a programming language owed much to Robert Kowalski, whose work with the Marseille group helped crystallize the approach.
Prolog became the leading language of European and Japanese AI research, and Japan chose it as the basis of its ambitious Fifth Generation computer project. It powered expert systems, natural-language interfaces, and theorem provers, and it remains in use today wherever rule-based reasoning and symbolic search fit the problem.
Why business readers should care: Prolog embodies declarative programming, describing what is true and letting the machine work out the consequences. That idea lives on in database query languages, business-rule engines, and the logic layers that check and enforce policies.