A derivative and redesign of APL with added features and control structures. J is purely functional with lexical scope and more conventional control structures, plus several new concepts such as function rank and function arrays. J was designed and developed by Kennneth E. Iverson and Roger Hui <email@example.com>. J uses only the ASCII character set but has a spelling scheme that retains the advantages of APL's special alphabet. J is a conventional procedural programming language but can be used as a purely functional language.
Version 4.1 for MS-DOS, Sun, Mac, Archimedes. Source available in C from Iverson Software, +1 (416) 925 6096.
Version 6 package from ISI includes an interpreter and tutorial. Ported to DEC, NeXT, SGI, Sun-3, Sun-4, Vax, RS/6000, MIPS, Macintosh, Acorn Archimedes, IBM PC, Atari, 3b1, Amiga.
J-mode GNU Emacs macros available by ftp://think.com/pub/j/gmacs/j-interaction-mode.el.
["APL\?", Roger K.W. Hui et al, APL90 Conf Proc, Quote Quad 20(4):192-200].