The SHARE Operating System (SOS) was created in 1959 as an improvement on the General Motors GM-NAA I/O operating system, the first operating system, by the SHARE user group. The main target was to improve the sharing of programs over GM-NAA I/O.
SHARE Operating System provided new methods to manage buffers and input/output devices, and, like GM-NAA I/O, allowed execution of programs written in assembly language.
Initially, it worked on IBM 709 computer and its transistorized compatible successor the IBM 7090.
A series of articles describing innovations in the system appears in the April, 1959, ACM Journal.
In 1962, IBM discontinued support for SOS and announced an entirely new (and incompatible) operating system IBM 7090/94 IBSYS.