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J (programming language)
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<p>The J <a href="/facts/Programming_language/cWTYbgWa">programming language</a>, developed in the early 1990s by <a href="/facts/Kenneth_E._Iverson/2K4c4hsh">Kenneth E. Iverson</a> and <a href="/facts/Roger_Hui/bsYdkhWv">Roger Hui</a>, is an <a href="/facts/Array_programming/gFx1SxIY">array programming</a> language based primarily on <a href="/facts/APL_/E2sb98gC">APL</a> (also by Iverson). </p><p>To avoid repeating the APL special-character problem, J uses only the basic <a href="/facts/ASCII/vGUI33Qu">ASCII</a> character set, resorting to the use of the dot and colon as <i>inflections</i> to form short words similar to <i><a href="/facts/Digraph_(computing)/EGyPjbls">digraphs</a></i>. Most such <i>primary</i> (or <i>primitive</i>) J words serve as mathematical symbols, with the dot or colon extending the meaning of the basic characters available. Also, many characters which in other languages often must be paired (such as [] {} "" `` or <>) are treated by J as stand-alone words or, when inflected, as single-character roots of multi-character words. </p><p>J is a very terse <a href="/facts/Array_programming_language/gFx1SxIY">array programming language</a>, and is most suited to <a href="/facts/Mathematical/pxTouaz4">mathematical</a> and <a href="/facts/Statistical/DNPsKGYU">statistical</a> programming, especially when performing operations on <a href="/facts/Matrix_(mathematics)/qa8FI4ko">matrices</a>. It has also been used in <a href="/facts/Extreme_programming/UCeJIvhQ">extreme programming</a> and <a href="/facts/Network_performance/ALjfw5Nn">network performance</a> analysis. </p><p>Like <a href="/facts/John_Backus/pqELHDh6">John Backus</a>'s languages <a href="/facts/FP_/mwLQ3D6t">FP</a> and <a href="/facts/FL_/EahaIaDo">FL</a>, J supports <a href="/facts/Function-level_programming/0uCybhfG">function-level programming</a> via its <i><a href="/facts/Tacit_programming/x8bU89wW">tacit programming</a></i> features. </p><p>Unlike most languages that support <a href="/facts/Object-oriented_programming/TxNMEcao">object-oriented programming</a>, J's flexible hierarchical <a href="/facts/Namespace/9efXwMtV">namespace</a> scheme (where every name exists in a specific <i>locale</i>) can be effectively used as a framework for both <a href="/facts/Class-based_programming/n3wudt1B">class-based</a> and <a href="/facts/Prototype-based_programming/x9oNIYPG">prototype-based</a> object-oriented programming. </p><p>Since March 2011, J is <a href="/facts/Free_and_open-source_software/1cHtjLCB">free and open-source software</a> under the <a href="/facts/GNU_General_Public_License/S75KhLSX">GNU General Public License</a> version 3 (GPLv3). One may also purchase source under a negotiated license. </p>