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Prolog (PROgrammation en LOGique) was designed in 1972 at the University of Marseille. It's a declarative language — you state what's true, not how to compute. The Prolog engine searches for proofs.

A minimal Judge0-runnable Prolog program needs an initialization directive:

:- initialization(main).

main :-
    write('Hello, Prolog!'),
    nl.

• :- initialization(main). tells Prolog to call main on startup
• A predicate is name :- body. (body uses , for AND, . to end)
• write/1 prints; nl outputs a newline
• Strings are typically atoms in single quotes in classic Prolog
• Comments use %

Variables start with uppercase or _. Lowercase identifiers are atoms (constants).