This article is about developing in C for CP/M, using a 40-year-old C compiler, and how this differs from modern C development. The compiler I’m using is the 1982 release of Manx Software Systems’ “Aztec C”. The compiler is freely, and legally, available from the Aztec Museum. A lot of CP/M software falls into the broad category of “abandonware” – software that is notionally still protected by intellectual propery law, but whose owners have no interest in it, or cannot even be identified.