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OCaml was designed in 1996 at INRIA (France). It's the granddaddy of ML-family languages — F#, Reason, and ReScript all descend from it. Used heavily in finance (Jane Street, Bloomberg) and proof assistants (Coq, Lean).

let () = print_endline "Hello, OCaml!"

• let () = ... is how you run a side-effect at top level. The () (unit) is OCaml's void.
• print_endline writes a string + newline.
• No semicolons at end of statements (but ;; separates top-level definitions in REPL).

OCaml is strict (eagerly evaluated, unlike Haskell), statically typed (every value has a known type at compile time), and type-inferred (you almost never write the type — the compiler figures it out).

Comments use (* ... *) and can nest.