Editing IBM System/360 (section)

{{Short description|IBM mainframe computer family (1964–1977)}}
{{Infobox computing device
| name         = System/360
| aka          = S/360
| logo         = IBM System 360 wordmark.svg|logo_upright=0.75
| image        = IBM System 360 model 30 profile.agr.jpg
| caption      = IBM System/360 Model 30 central processor unit (CPU)
| developer    = [[IBM]]
| manufacturer = IBM
| release date = {{Start date and age|1964|04|07}}
| family       = See [[#Table of System/360 models|table of models]]
| discontinued = {{End date and age|1978}}
| type         = [[Mainframe computer]]
| memory       = 8 KB – 9 MB
| RAMtype      = [[Magnetic-core memory|core memory]])<br>([[thin-film memory]] on the Model 95)
| predecessor  = [[IBM 700/7000 series|700/7000 series]]
| successor    = [[IBM System/370|System/370]]
| os           = {{hlist|[[BOS/360]]|[[TOS/360]]|[[DOS/360]]|[[OS/360]]|[[TSS/360]]}}
| related      = [[IBM System/360 architecture|System/360 architecture]]
| media        = {{hlist|[[7-track tape]]|[[9-track tape]]|[[direct-access storage device|DASD]]s|[[paper tape]]|[[Printer (computing)|printed paper]]|[[punched card]]s}}
}}

{{IBM mainframes}}

The '''IBM System/360''' ('''S/360''') is a family of [[mainframe computer]] systems announced by [[IBM]] on April 7, 1964,<ref name="Padegs"/> and delivered between 1965 and 1978.<ref>{{cite web|url=http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_FS360.html|archive-url=https://web.archive.org/web/20050116150036/http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_FS360.html|url-status=dead|archive-date=January 16, 2005|title=IBM System/360 Dates and Characteristics|publisher=[[IBM]]|date=2003-01-23}}</ref> System/360 was the first family of computers designed to cover both commercial and scientific applications and a complete range of applications from small to large. The design distinguished between [[computer architecture|architecture]] and implementation, allowing IBM to release a suite of compatible designs at different prices. All but the only partially compatible [[IBM System/360 Model 44|Model 44]] and the most expensive systems use [[microcode]] to implement the instruction set, featuring [[8-bit computing|8-bit]] byte addressing and fixed-point binary, fixed-point decimal and [[IBM hexadecimal floating-point|hexadecimal]] [[floating-point arithmetic|floating-point]] calculations. The System/360 family introduced IBM's [[Solid Logic Technology]] (SLT), which packed more transistors onto a circuit card, allowing more powerful but smaller computers.<ref>{{cite web |last=Clarke |first=Gavin |date=April 7, 2014 |title=Why won't you DIE? IBM's S/360 and its legacy at 50 |url=https://www.theregister.com/2014/04/07/ibm_s_360_50_anniversary/ |website=[[The Register]]}}</ref>

System/360's chief architect was [[Gene Amdahl]], and the project was managed by [[Fred Brooks]], responsible to Chairman [[Thomas J. Watson Jr.]]<ref name="PA">{{cite press release |title=System/360 Announcement |date=April 7, 1964 |publisher=IBM Data Processing Division |url=http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PR360.html |quote=...machine cycle time ... ranges from one millionth-of-a-second to only 200 billionths-of-a-second. ... memory capacity ranges from 8,000 characters of information to more than 8,000,000. |url-status=dead |archive-url=https://web.archive.org/web/20050114203048/http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PR360.html |archive-date=2005-01-14 |id=IBM-PR360}}</ref> The commercial release was piloted by another of Watson's lieutenants, [[John R. Opel]], who managed the launch of IBM's System/360 mainframe family in 1964.<ref>{{cite web |date=24 October 2018 |title=IBM - Former CEO John Opel - An Appreciation |url=http://www.ibm.com/ibm/us/en/johnopel.html |website=IBM}}</ref> The slowest System/360 model announced in 1964, the [[IBM System/360 Model 30|Model 30]], could perform up to 34,500 instructions per second, with memory from 8 to 64&nbsp;[[Kibibyte|KB]].<ref>{{cite web|url=http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2030.html|archive-url=https://web.archive.org/web/20041217213638/http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2030.html|url-status=dead|archive-date=December 17, 2004|title=System 360/30 announcement|publisher=IBM|date=2003-01-23}}</ref> High-performance models came later. The 1967 [[IBM System/360 Model 91]] could execute up to 16.6 [[million instructions per second]].<ref>{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2091.html|title=System/360 Model 91|publisher=IBM|date=2003-01-23|archive-url=https://web.archive.org/web/20190702195149/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2091.html|archive-date=2019-07-02}}</ref> The larger 360 models could have up to 8&nbsp;[[Mebibyte|MB]] of [[main memory]],<ref name="PA" /> though that much memory was unusual; a large installation might have as little as 256&nbsp;KB of main storage, but 512&nbsp;KB, 768&nbsp;KB or 1024&nbsp;KB was more common. Up to 8 megabytes of slower (8 microsecond) [[IBM 2361 Large Capacity Storage|Large Capacity Storage (LCS)]] was also available for some models.

The IBM 360 was extremely successful, allowing customers to purchase a smaller system knowing they could expand it, if their needs grew, without reprogramming application software or replacing peripheral devices. It influenced computer design for years to come; many consider it one of history's most successful computers. Application-level compatibility (with some restrictions) for System/360 software is maintained to the present day with the [[IBM System z|System z]] mainframe servers.