Editing History of operating systems (section)

==Mainframes==
The first operating system used for real work was [[GM-NAA I/O]], produced in 1956 by [[General Motors]]' Research division<ref>{{cite web
 | url       = https://www.rand.org/content/dam/rand/pubs/papers/2008/P7316.pdf
 | title     = General Motors/North American Monitor for the IBM 704 Computer
 | publisher = [[RAND Corporation]]
 | author    = Robert Patrick
 | date      = January 1987}}</ref> for its [[IBM 704]].<ref name="CHM-1956-SW">{{cite web
 | url        = http://www.computerhistory.org/timeline/?year=1956
 | title      = Timeline of Computer History: 1956: Software
 | publisher  = [[Computer History Museum]]
 | access-date = 2008-05-25}}</ref>{{Specify|reason=Cited link has no mention of GM-NAA IO or IBM 704 at all|date=March 2020}} Most other early operating systems for IBM mainframes were also produced by customers.<ref name="bozemanlugHistoryOfLinux">{{cite web
 | url          = http://bozemanlug.montanalinux.org/talks/linux_history.html
 | title        = A Brief History of Linux
 | access-date  = 2017-11-05
 | archive-url  = https://web.archive.org/web/20171107022354/http://bozemanlug.montanalinux.org/talks/linux_history.html
 | archive-date = 2017-11-07
 | url-status   = dead}}</ref>

Early operating systems were very diverse, with each vendor or customer producing one or more operating systems specific to their particular [[mainframe computer]]. Every operating system, even from the same vendor, could have radically different models of commands, operating procedures, and such facilities as debugging aids. Typically, each time the manufacturer brought out a new machine, there would be a new operating system, and most applications would have to be manually adjusted, recompiled, and retested.

===Systems on IBM hardware===
{{main|History of IBM mainframe operating systems}}

The state of affairs continued until the 1960s when [[IBM]], already a leading hardware vendor, stopped work on existing systems and put all its effort into developing the [[IBM System/360|System/360]] series of machines, all of which used the ''same'' instruction and input/output architecture. IBM intended to develop a single operating system for the new hardware, the [[OS/360 and successors|OS/360]]. The problems encountered in the development of the OS/360 are legendary, and are described by [[Fred Brooks]] in ''[[The Mythical Man-Month]]''—a book that has become a classic of [[software engineering]]. Because of performance differences across the hardware range and delays with software development, a whole family of operating systems was introduced instead of a single OS/360.<ref name="JohnsonVSEPast40Years">{{cite journal
 | last        = Johnston
 | date        = April 1, 2005
 | title       = VSE: A Look at the Past 40 Years
 | journal     = z/Journal
 | issue       = April/May 2005
 | publisher   = Thomas Communications, Inc.
 | url         = http://www.zjournal.com/index.cfm?section=article&aid=293
 | url-status  = dead
 | archive-url  = https://web.archive.org/web/20090304014628/http://www.zjournal.com/index.cfm?section=article&aid=293
 | archive-date = March 4, 2009}}</ref><ref name="Boyer360Revolution">{{cite web |author=Chuck Boyer |url=https://www.vm.ibm.com/history/360rev.pdf |title=The 360 Revolution}}</ref>

IBM wound up releasing a series of stop-gaps followed by two longer-lived operating systems:
* [[OS/360 and successors|OS/360]] for mid-range and large systems. This was available in three [[System Generation (OS)|system generation]] options:
** [[OS/360 and successors#PCP|PCP]] for early users and for those without the resources for multiprogramming.
** [[OS/360 and successors#MFT|MFT]] for mid-range systems, replaced by MFT-II in OS/360 Release 15/16. This had one successor, [[OS/VS1]], which was discontinued in the 1980s.
** [[OS/360 and successors#MVT|MVT]] for large systems. This was similar in most ways to PCP and MFT (most programs could be ported among the three without being [[compiler|re-compiled]]), but has more sophisticated memory management and a [[time-sharing]] facility, [[Time Sharing Option|TSO]]. MVT had several successors including the current [[z/OS]].
* [[DOS/360 and successors|DOS/360]] for small System/360 models had several successors including the current [[VSE (operating system)|z/VSE]]. It was significantly different from OS/360.

IBM maintained full compatibility with the past, so that programs developed in the sixties can still run under z/VSE (if developed for DOS/360) or z/OS (if developed for MFT or MVT) with no change.

IBM also developed [[TSS (operating system)|TSS/360]], a time-sharing system for the [[IBM System/360 Model 67|System/360 Model 67]]. Overcompensating for their perceived importance of developing a timeshare system, they set hundreds of developers to work on the project. Early releases of TSS were slow and unreliable; by the time TSS had acceptable performance and reliability, IBM wanted its TSS users to migrate to OS/360 and OS/VS2; while IBM offered a TSS/370 PRPQ, they dropped it after 3 releases.<ref>{{cite web |url=http://www.beagle-ears.com/lars/engineer/comphist/ibm360.htm |title=IBM 360/370/3090/390 |author=Lars Poulsen |date=26 October 2001 |work=Computer History |access-date=18 November 2015}}</ref>

Several operating systems for the IBM S/360 and S/370 architectures were developed by third parties, including the [[Michigan Terminal System]] (MTS) and [[MUSIC/SP]].

===Other mainframe operating systems===
[[Control Data Corporation]] developed the [[CDC SCOPE|SCOPE]] operating systems<ref group=NB>CDC used the SCOPE name for disparate operating systems on the [[CDC 3000|upper 3000 series]], the [[CDC 3000|lower 3000 series]], the [[CDC 6000 series|6000 series]] and the [[CDC 7600|7600]]</ref> in the 1960s, for [[batch processing]] and later developed the [[CDC Kronos|MACE]] operating system for time sharing, which was the basis for the later [[CDC Kronos|Kronos]]. In cooperation with the [[University of Minnesota]], the Kronos and later the [[NOS (operating system)|NOS]] operating systems were developed during the 1970s, which supported simultaneous batch and time sharing use. Like many commercial time sharing systems, its interface was an extension of the [[Dartmouth Time-Sharing System|DTSS]] time sharing system, one of the pioneering efforts in timesharing and programming languages.

In the late 1970s, Control Data and the [[University of Illinois at Urbana–Champaign|University of Illinois]] developed the [[PLATO (computer system)|PLATO system]], which used plasma panel displays and long-distance time sharing networks. PLATO was remarkably innovative for its time; the shared memory model of PLATO's [[TUTOR (programming language)|TUTOR programming language]] allowed applications such as real-time chat and multi-user graphical games.

For the [[UNIVAC 1100/2200 series#1107|UNIVAC 1107]], [[UNIVAC]], the first commercial computer manufacturer, produced the [[UNIVAC EXEC I|EXEC I]] operating system, and [[Computer Sciences Corporation]] developed the [[UNIVAC EXEC II|EXEC II]] operating system and delivered it to UNIVAC. EXEC II was ported to the [[UNIVAC 1100/2200 series#1108|UNIVAC 1108]]. Later, UNIVAC developed the [[OS 2200#Exec 8|EXEC 8]] operating system for the 1108; it was the basis for operating systems for later members of the family. Like all early mainframe systems, EXEC I and EXEC II were a batch-oriented system that managed magnetic drums, disks, card readers and line printers; EXEC 8 supported both batch processing and on-line transaction processing. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the [[Dartmouth BASIC]] system.

[[Burroughs Corporation]] introduced the [[Burroughs large systems|B5000]] in 1961 with the MCP ([[Burroughs MCP|Master Control Program]]) operating system. The B5000 was a stack machine designed to exclusively support high-level languages, with no software, not even at the lowest level of the operating system, being written directly in [[machine language]] or [[assembly language]]; the MCP was the first{{Citation needed|reason=Did ESPOL precede NELIAC?|date=November 2014}} OS to be written entirely in a high-level language - [[Executive Systems Problem Oriented Language|ESPOL]], a dialect of [[ALGOL 60]] - although ESPOL had specialized statements for each "syllable"<ref group=NB>A syllable in the B5000 could contain a 10-bit [[Literal (computer programming)|literal]], an [[operand]] call, a [[Burroughs large systems descriptors|descriptor]] call or a 10-bit [[opcode]].</ref> in the B5000 instruction set. MCP also introduced many other ground-breaking innovations, such as being one of<ref group=NB>The B5000 was contemporaneous with the [[Ferranti]] [[Atlas Computer (Manchester)|Atlas]]</ref> the first commercial implementations of [[virtual memory]]. The rewrite of MCP for the B6500 is now marketed as the [[Unisys]] ClearPath/MCP.

[[General Electric|GE]] introduced the [[GE-600 series]] with the [[General Comprehensive Operating System|General Electric Comprehensive Operating Supervisor]] (GECOS) operating system in 1962. After [[Honeywell]] acquired GE's computer business, it was renamed to General Comprehensive Operating System (GCOS). Honeywell expanded the use of the GCOS name to cover all its operating systems in the 1970s, though many of its computers had nothing in common with the earlier GE 600 series and their operating systems were not derived from the original GECOS.

[[MIT Computer Science and Artificial Intelligence Laboratory#Project MAC|Project MAC]] at MIT, working with GE and [[Bell Labs]], developed [[Multics]], which introduced the concept of ringed security privilege levels.

[[Digital Equipment Corporation]] developed [[TOPS-10]] for its [[PDP-10]] line of 36-bit computers in 1967. Before the widespread use of Unix, TOPS-10 was a particularly popular system in universities, and in the early [[ARPANET]] community. [[BBN Technologies|Bolt, Beranek, and Newman]] developed [[TENEX (operating system)|TENEX]] for a modified PDP-10 that supported [[demand paging]]; this was another popular system in the research and ARPANET communities, and was later developed by DEC into [[TOPS-20]].

[[Scientific Data Systems]]/Xerox Data Systems developed several operating systems for the [[SDS Sigma series|Sigma series]] of computers, such as the Basic Control Monitor (BCM), Batch Processing Monitor (BPM), and Basic Time-Sharing Monitor (BTM). Later, BPM and BTM were succeeded by the [[Universal Time-Sharing System]] (UTS); it was designed to provide multi-programming services for online (interactive) user programs in addition to batch-mode production jobs, It was succeeded by the [[CP-V]] operating system, which combined UTS with the heavily batch-oriented [[Xerox Operating System]].