Extensively used within the Mathematica system itself, MathLink is Mathematica's unique high-level symbolic interface standard for interprogram communication. With convenient bindings for a variety of languages, MathLink immediately allows arbitrary symbolic objects—representing data, programs, or any other construct—to be efficiently exchanged between programs, on one computer or across a heterogeneous network.
Install — run a MathLink installable external program
LinkPatterns — find functions available in a running MathLink program
Links — list all currently open links