Forth (programming language)
Forth is a procedural, stack-oriented programming language and interactive environment designed by Charles H. "Chuck" Moore and first used by other programmers in 1970. Although not an acronym, the language's name in its early years was often spelled in all capital letters as FORTH. Forth combines a compiler with an integrated multitasking command shell, where the user interacts via subroutines called words. Words can be defined, tested, redefined, and debugged without recompiling or restarting the whole program. All syntactic elements, including variables and basic operators, are defined as words. A stack is used to pass parameters between words, leading to a Reverse Polish Notation style. For much of Forth's existence, the standard technique was to compile to threaded code, which can be interpreted faster than bytecode. One of the early benefits of Forth was size: an entire development environment—including compiler, editor, and user programs—could fit in memory on an 8-bit or similarly limited system. No longer constrained by space, there are modern implementations that generate optimized machine code like other language compilers. Forth is used in the Open Firmware boot loader, in space applications such as the Philae spacecraft, and in other embedded systems which involve interaction with hardware. The relative simplicity of creating a basic Forth system has led to many personal and proprietary variants, such as the custom Forth used to implement the bestselling 1986 video game Starflight from Electronic Arts. The free software Gforth implementation is actively maintained, as are several commercially supported systems. Moore later developed a series of microprocessors for executing compiled Forth-like code directly and experimented with smaller languages based on Forth concepts, including cmForth and colorForth. (Wikipedia).
