Action! (programming language)

Action! is a procedural programming language and integrated development environment written by Clinton Parker for the Atari 8-bit computers. Its syntax is close to ALGOL and its constructs were designed to map cleanly onto the opcodes of the MOS Technology 6502, so a simple one-pass compiler could produce fast programs without heavy optimisation; local variables sit at fixed addresses rather than on a stack, which makes fast code but rules out recursion. The data types are all numeric, namely BYTE, CARD and INT, with arrays, pointers and user-defined types and no floating point. Parker had earlier built Micro-SPL, a systems language for the Xerox Alto, with Henry Baker, and Action! is largely a port of those ideas to the Atari with a fullscreen editor and monitor added. Optimized Systems Software sold it on a bank-switched 16 kB ROM cartridge from 1983, reviewers praised its speed, and Parker released its assembly source under the GNU General Public License in 2015.