A brief review of APL, its origins and what makes it distinctive.

Conventional programming languages set out to describe and control computer operations. At Harvard in the 1950s Ken Iverson was revising traditional mathematical notation. He wanted a consistent language for describing operations on arrays, a notation a machine could interpret.

Iverson was a key member of the early computer science community. At Harvard with Howard Aiken he taught the world’s first classes on computing. When he published his math notation, he titled the book A Programming Language (Wiley, New York, 1962). His teaching assistant at Harvard, Fred Brooks, author of <cite>The Mythical Man Month</cite>, was IBM’s project manager for the development of OS/360, its first multi-tasking operating system. (OS/360 was the first operating system ever described formally — in Iverson notation, of course.) Iverson also went to IBM, who made him a Research Fellow, and implemented his notation on an 1130 computer, where it was dubbed APL after the title of his book. APL\1130 was providing personal computing to a community of users well before OS/360 came to life.