A+

A+ is an extension of the A language. A was created in 1985 by Arthur Whitney, then of Morgan Stanley. At the time, various departments had a significant investment in APL applications and talent, APL being a language well-suited to the manipulation of large arrays of numbers. As technology was moving from the mainframe to distributed systems, there was a search for a suitable APL implementation to run on SunOS, the distributed platform of the period, and this prompted Whitney to create A as a statically typed dialect of APL with various novelties like symbols as a simple scalar type and the Rank operator.

Over the course of the next few years, various extensions were made to the language, culminating in A+ in 1988, with "+" referring to the graphical user interface. While an A+ development group was formally in 1992, presented the very first version of K that very same year, and by 1994, K became the official successor of A+. In 2001, the source code was made public, and various volunteers took over development until 2008. From then until 2014 it was maintained by Robert Lefkowitz.