GAP is a system for computational discrete algebra, with particular emphasis on computational group theory. GAP provides a programming language, a library of thousands of functions implementing algebraic algorithms written in the GAP language as well as large data libraries of algebraic objects. For a more detailed overview, see https://www.gap-system.org/Overview/overview.html. For a description of the mathematical capabilities, see https://www.gap-system.org/Overview/Capabilities/capabilities.html. GAP is used in research and teaching for studying groups and their representations, rings, vector spaces, algebras, combinatorial structures, and more. The system, including source, is distributed freely. You can study and easily modify or extend it for your special use.