Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Forth (programming language)
open-in-new
<p>Forth is a <a href="/facts/Stack-oriented_programming/RFhFMhuj">stack-oriented</a> <a href="/facts/Programming_language/cWTYbgWa">programming language</a> and interactive <a href="/facts/Integrated_development_environment/jbEINSQf">integrated development environment</a> designed by <a href="/facts/Charles_H._Moore/9rsgu4PF">Charles H. "Chuck" Moore</a> and first used by other programmers in 1970. Although not an <a href="/facts/Acronym/nlHK7aRt">acronym</a>, the language's name in its early years was often spelled in <a href="/facts/All_caps/ASFdydxp">all capital letters</a> as <i>FORTH</i>. The FORTH-79 and FORTH-83 implementations, which were not written by Moore, became <i><a href="/facts/De_facto/3Du6WQKh">de facto</a></i> standards, and an official <a href="/facts/Technical_standard/P4orT1SM">technical standard</a> of the language was published in 1994 as ANS Forth. A wide range of Forth derivatives existed before and after ANS Forth. The <a href="/facts/Free_and_open-source_software/1cHtjLCB">free and open-source software</a> <a href="/facts/Gforth/69PxhhNT">Gforth</a> implementation is actively maintained, as are several <a href="/facts/Commercial_software/WLgyRFMh">commercially</a> supported systems. </p><p>Forth typically combines a compiler with an integrated command shell, where the user interacts via <a href="/facts/Subroutine/9vFJrg0A">subroutines</a> called <i>words</i>. Words can be defined, tested, redefined, and debugged without recompiling or restarting the whole program. All syntactic elements, including variables, operators, and control flow, are defined as words. A <a href="/facts/Stack_(abstract_data_type)/bj7l94v1">stack</a> is used to pass parameters between words, leading to a <a href="/facts/Reverse_Polish_notation/a6rDoJ7X">Reverse Polish notation</a> style. </p><p>For much of Forth's existence, the standard technique was to compile to <a href="/facts/Threaded_code/RwL3h6DJ">threaded code</a>, which can be interpreted faster than <a href="/facts/Bytecode/EPkMFR7M">bytecode</a>. 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 <a href="/facts/Optimizing_compiler/JXnv4LUd">optimized</a> <a href="/facts/Machine_code/bgdQ1Fxf">machine code</a> like other language compilers. 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 <i><a href="/facts/Starflight/zr83ewJs">Starflight</a></i> from <a href="/facts/Electronic_Arts/fy7Ppdem">Electronic Arts</a>. </p><p>Forth is used in the <a href="/facts/Open_Firmware/M9e578XY">Open Firmware</a> <a href="/facts/Boot_loader/6sNpcLMK">boot loader</a>, in <a href="/facts/Spaceflight/zPrnATzo">spaceflight</a> applications such as the <a href="/facts/Philae_(spacecraft)/MzUzq8f0"><i>Philae</i> spacecraft</a>, and in other embedded systems which involve interaction with hardware. </p><p>Moore developed a series of microprocessors for executing compiled Forth-like code directly and experimented with smaller languages based on Forth concepts, including cmForth and <a href="/facts/ColorForth/VzoPcDse">colorForth</a>. Most of these languages were designed to support Moore's own projects, such as chip design. </p>