Version 2.1.o (before 1995-10-30).
2. A Unix command interpreter shell by Paul Falstad <email@example.com> some time before 1993-03-23. It is similar to, but not completely compatible with, ksh, with many additions to please csh users and some tcsh features. zsh supports editing of multi-line commands in a single buffer; variable editing; a command buffer stack; recursive globbing; manipulation of arrays; and spelling correction.