 A COS batch job would be submitted to start up UNICOS, which would then run as a subsystem under COS - using a subset of the systems CPUs, memory, and peripheral devices.The UNICOS that ran under GOS was exactly the same as when it ran stand-alone - the difference was that the kernel would make certain low-level hardware requests through the COS GOS hook, rather than directly to the hardware.One of the sites that ran very early versions of UNICOS was Bell Labs, where Unix pioneers including Dennis Ritchie ported parts of their Eighth Edition Unix (including stream I/O) to UNICOS.