''A+ is a descendant of APL (AplLanguage) and a predecessor of K (KayLanguage)'' 

ArthurWhitney developed A+ in the late '80s in response to employer Morgan Stanley's need to move their APL applications from mainframes to Sun workstations
* A+ is open source
** homepage 
*** http://www.aplusdev.org/
** XEmacs (EmacsEditor) is the main development environment for A+, through a Lisp extension and a special font. 
** The extension sets up a simple two-pane layout with an upper area for reading text files and for storing code, and a lower portion for an interactive session, like DrScheme. 
** It's necessary to fiddle with xmodmap in order to type special characters.
** There are no high-level facilities for doing Unix-style CLI input and output, which is a little surprising for a Unix-only, open source system. 
** C libraries can be used, and A+ provides direct access to Unix system calls, so command-line interfaces are possible but not practical. A+ applications were expected to communicate through the interesting declarative GUI built into the language. (It's in Motif, so it looks fairly dated on modern systems.)
** While the author went on to write K after leaving Morgan Stanley, interested parties might take more interest in JayLanguage, which is closer to the AplLanguage origins.
* --JesseMillikan
** reference manual
*** http://www.aplusdev.org/refman.html
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CategoryProgrammingLanguage