The Free On-line Dictionary of Computing (18 March 2015):
The generic name for the CPUs and architecture
released by IBM on 1964-04-07. The 360 was marketed as a
general purpose computer with 'all round' functionality -
hence 360 (degrees).
Models ranged from the 360/20 to the 360/65 and later the
360/95, with typical memory configurations from 16K to 1024K.
Elements of the architecture, such as the basic instruction
set are still in use on IBM mainframes today. Operating
System/360 (OS/360) was developed for System/360. Other
associated operating systems included DOS, OS/MFT and
The 360 architecture was based on an 8-bit byte, 16 general
purpose registers, 24-bit addressing, and a PSW (Program
Status Word) including a location counter.
Gene Amdahl, then an IBM employee, is generally acknowledged
as the 360's chief architect. He later went on to found
Amdahl Corporaton, a manufacture of PCM mainframe
The 360's predecessors were the smaller IBM 1401 and the large
IBM 7090 series. If was followed by the System/370.
See also ABEND, ALC, BAL, Big Red Switch, HCF, mode
bit, PL360, PL/S.