GECOS is/was an operating system developed by General Electric in the early sixties. It stands for GE Comprehensive Operating System. It was designed to run on some sort of GE mainframe.

In the late sixties, a newer version of the same mainframe was selected by Bell Laboratories to use as the platform for the Multics project. You can see where this is headed.

GE was then bought out by Honeywell, who promptly dropped the E in the name, and it became GCOS (for General Comprehensive...). There was a war between the GCOS and Multics crews, and GCOS won, which led to the demise of Multics.

When the Multics project got canned, a couple of bright engineers thought it would be fun to hack some rudimentary OS tools on a discarded PDP-7 minicomputer... Some early Unix systems running at Bell ran on GCOS hardware, or else they talked to them, I'm not sure which. In any event the information needed to connect to them was stored in what was referred to as the GECOS field. And there you have it.

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