This document is an introduction to ML programming, specifically for the Objective Caml (OCaml) programming language from INRIA. OCaml is a dialect of the ML (Meta-Language) family of languages, which derive from the Classic ML language designed by Robin Milner in 1975 for the LCF (Logic of Computable Functions) theorem prover. OCaml shares many features with other dialects of ML, and it provides several new features of its own. Throughout this document, we use the term ML to stand for any of the dialects of ML, and OCaml when a feature is specific to OCaml.

ML is a functional language, meaning that functions are treated as first-class values. Functions may be nested, functions may be passed as arguments to other functions, and functions can be stored in data structures. Functions are treated like their mathematical counterparts as much as possible. Assignment statements that permanently change the value of certain expressions are permitted, but used much less frequently than in languages like Cor JAVA.