What is 'Prolog'?
Prolog is a programming language that is based on first order logic. A Prolog program consists of a set of facts and a set of rules. It received a lot of interest in the late 1980s as many experts believed it could become one of the most popular and important programming languages. Certainly, the ability to express problems declaratively and leave it to the computer to work out some of the procedural details seemed very appealing. But when using Prolog in practice, there are times when you simply cannot avoid the procedural aspects of computing.
Prolog never became very popular in practice, and remained largely a programming language for academics, expecially researchers in Artificial Intelligence. It remains a very important language for the expression of constraint problems in constraint logic programming
In truth, many people find it difficult to program in Prolog, as it requires a different way of thinking to other "conventional" programming languages.