FORTH - technical definition

(FOuRTH-generation language) A high-level programming language created by Charles Moore in the late 1960s as a way of providing direct control of the computer. Its syntax resembles LISP, it uses reverse polish notation for calculations, and it is noted for its extensibility.

It is both compiler and interpreter. The source program is compiled first and then executed by its operating system/interpreter. It is used in process control applications that must quickly process data acquired from instruments and sensors. It is also used in arcade game programming as well as robotics and other AI applications. The following polyFORTH example converts Fahrenheit to Celsius:

   : CONV ( n) 32 - 5 9 * / . ." Celsius
   : USER_INPUT  ." Enter Fahrenheit " CONV ;