/jee'kohs/ An operating system developed by General Electric from 1962; originally called GECOS (the General Electric Comprehensive Operating System). Some early Unix systems at Bell Labs used GCOS machines for print spooling and various other services. The field added to "/etc/passwd" to carry GCOS ID information was called the "GECOS field" and survives today as the "pw_gecos" member used for the user's full name and other human-ID information.