(IPL) Said to be the first list-processing language, also the first language to support recursion. Written by Allen Newell, J.C. Shaw and H. Simon at Carnegie ca. 1956. It was very low level.

Versions: IPL-I (never implemented), IPL-II (1957 for JOHNNIAC), IPL-III (existed briefly), IPL-IV, IPL-V (1958, for IBM 650, IBM 704, IBM 7090, many others. Widely used), IPL-VI.

[Sammet 1969, pp. 388-400].

["Information Processing Language-V Manual", A. Newell ed, P-H 1965].