C was alongside Assembly the most important programming language on the Amiga. The Amiga operating system itself is written in C (with Assembly for time-critical parts). The Amiga system includes define all OS structures and functions. Important concepts: library calls via jump tables (e.g. OpenLibrary(), AllocMem()), message passing between processes (Exec messages), TagItem-based function calls (from OS 2.0). The Amiga C API was ahead of its time with features like shared libraries, message ports, and multitasking.