Q was a test-bed for programming language ideas. Where APL uses arrays for looping, Q uses generalised sequences which may be infinite and may be stored or calculated on demand. It has macros, primitives to run programs, and an interactive command language.
Q is implemented in C++, and comes with an interpreter, compiler framework, libraries, and documentation. It runs on Linux and SUN-4 and should work on any 32-bit Unix.
Latest version: 1, as of 1993-06-07. Development stopped in 1994.