Editing DOS/360 and successors (section)

==DOS versions==

===BOS/360===
{{main|BOS/360}}
The '''Basic Operating System''' (BOS) was an early version of DOS and TOS which could provide usable functionality on a system with as little as 8&nbsp;KB of main storage and one 2311 disk drive.<ref>{{cite book |last1=IBM Corporation |title=IBM System/36D Basic Operating System Programmer's Guide |date=Sep 1967 |url=http://bitsavers.org/pdf/ibm/360/bos_bps/C24-3372-6_BOSpgmr_Sep67.pdf |access-date=Jan 24, 2022}}</ref>

===TOS/360===
'''TOS/360''' (Tape Operating System/360, not a DOS as such and not so called) was an [[IBM]] [[operating system]] for the [[System/360]], used in the early days around 1965 to support the [[IBM System/360 Model 30|System/360 Model 30]] and similar platforms.

TOS, as per the "Tape" in the name, required a tape drive. It shared most of the code base<ref name=40Y.mem>{{cite newsgroup|url=https://groups.google.com/d/msg/alt.folklore.computers/RZA6FD27Tc0/-LoIXsOee7gJ|title=DOS/360: Forty years|author=Joe Morris|newsgroup=alt.folklore.computer|date=April 25, 2005|quote=Don't forget TOS, the bastard cousin of DOS.  Either could be generated from the same set of distribution libraries...}}</ref> and some manuals<ref>{{cite web|url=http://www.bitsavers.org/pdf/ibm/360/dos/GC24-5030-8_Disk_and_Tape_Operating_Systems_Concepts_and_Facilities_Oct70.pdf|title=IBM System/360 Disk and Tape Operating Systems Concepts and Facilities|date=October 1970|id=GC2ij-5030-8}}</ref><ref>{{cite web|url=http://www.bitsavers.org/pdf/ibm/360/dos/GC24-3465-8_DOS_and_TOS_Utility_Programs_R26.1_Aug73.pdf|title=DOS and TOS Utility Programs|date=August 1973|id=GC24-3465-8}}</ref> with IBM's DOS/360.

TOS went through 14 releases, and was discontinued<ref>{{cite mailing list|url=https://www.mail-archive.com/ibmvm@listserv.uark.edu/msg24371.html|author=Anne and Lynn Wheeler|title=Re: IBM 1401|date=May 28, 2009|mailing-list=ibmvm@listserv.uark.edu}}</ref>{{failed verification|date=July 2019}} when disks such as the [[IBM 2311]] and [[IBM 2314]] became more affordable at the time of System/360,<ref>{{cite magazine|magazine=Computerworld|date=September 5, 1977|volume=11|issue=36|pages=39–40|title=IBM Feared Competition to 360/30 CPU|url=https://books.google.com/books?id=nAq5oP06EfEC&pg=PA39}}</ref>{{failed verification|date=July 2019}} whereas they had been an expensive luxury on the [[IBM 7090]].

===DOS/360===
'''DOS/360''' was the primary operating system for most small to midsize S/360 installations.

===DOS/VS===
'''DOS/VS''' was released in 1972.  The first DOS/VS release was numbered "Release 28" to signify an incremental upgrade from DOS/360.<ref name=Boeblingen>{{cite web|last=IBM Corporation |title=IBM Geschichte im Jahr 1970 |url=http://www-05.ibm.com/de/entwicklung/1970.html |access-date=May 31, 2012 |language=de }}</ref> It added [[virtual memory]] in support of the new [[System/370]] series hardware.  It used a fixed [[page table]] which mapped a single [[address space]] of up to 16 megabytes for all partitions combined.

DOS/VS increased the number of partitions (separate simultaneous programs) from three (named Background, Foreground 1 and Foreground 2) to five (BG and F1 through F4) and allowed a system wide total of fifteen subtasks.<ref name=GC33-5370>{{cite book|last=IBM Corporation|title=Introduction to DOS/VS Release 29|year=1973}}GC33-5370-2</ref>{{rp|pp.24–28}}

DOS/VS was succeeded by DOS/VSE through [[VSE (operating system)|z/VSE]].

===DOS/VSE===
'''DOS/VSE''' was introduced in 1979 as an "extended" version of DOS/VS to support the new [[IBM 4300|4300]] processors.<ref name=StateOfTheUnion>{{cite journal|title=The VSE Operating System State of the Union|journal=z/Journal|date=November 1, 2008|url=http://enterprisesystemsmedia.com/article/the-vse-operating-system-state-of-the-union|access-date=September 18, 2019|archive-url=https://web.archive.org/web/20180304055413/http://enterprisesystemsmedia.com/article/the-vse-operating-system-state-of-the-union|archive-date=March 4, 2018}}</ref>
The [[IBM 4300|4300]] systems included a feature called ECPS:VSE that provided a single-level storage for both the processor and the I/O channels.<ref>{{cite book
 |author       = IBM
 |title        = IBM 4300 Processors Principles of Operation for ECPS:VSE Mode
 |version      = First edition
 |date         = January 1979
 |url          = http://www.bitsavers.org/pdf/ibm/4300/GA22-7070-0_4300_ECPS_VSE_Mode_Principles_Of_Operation_Jan79.pdf
 |id           = SA22-7070-0
}}</ref> DOS/VSE provided support for ECPS:VSE, but could also run on a System/370 without that feature. VSE was the last free version of DOS.

===VSE/AF===

'''VSE/Advanced Functions'''<ref>{{cite book
 | title       = VSE/Advanced Functions Program Summary
 | id          = GC33-6157-0
 | quote       = Together with the DOS/VSE SCP (system control programming), VSE/Advanced Functions provides operating system support for IBM processing units listed in the "Machine Requirements" section.
 | url         = http://bitsavers.org/pdf/ibm/370/DOS_VSE/GC33-6157-0_IBM_VSE_Advanced_Functions_Program_Summary_V1R3M5_5746-XE8_198306.pdf
 | access-date = January 24, 2022
 | publisher   = IBM
 }}
</ref> (VSE/AF), prepared for 1983 delivery, added new device support and functionality to DOS/VSE. Many installations ran VSE/AF using products such as VSE System Installation Productivity Option/Extended (VSE System IPO/E), which combined DOS/VSE, VSE/AF and various other products.

===SSX/VSE===
[[Image:IBM Böblingen Entwicklung und Forschung briefing center during installation1984.jpg|thumb|right|An IBM staffer installing a third-party application running on SSX/VSE, at the IBM Böblingen facility where SSX work was done]]
'''SSX/VSE''' ("Small System Executive") was an attempt by IBM to simplify purchase and installation of VSE by providing a pre-generated system containing the OS and the most popular products.<ref>{{Cite journal|date=1 Oct 1984|title=IBM adds SSX/VSE aid; offers DS/VSE frontend|url=https://books.google.com/books?id=qpTn_XtzdAMC&pg=PA46|journal=Computerworld|volume=18|issue=40|pages=46}}</ref>  SSX was released in 1982,<ref>{{Cite journal|last=Paul|first=Louis|date=23 Nov 1981|title=IBM brings out simplified operating system|url=https://books.google.com/books?id=94T9BTjdzT0C&pg=PA7|journal=Computerworld|volume=15|issue=47|pages=7}}</ref> and later replaced by VSE/SP. SSX was sold by IBM as a bundle of 14 component products (Advanced Functions/VSE, VSE/POWER, ACF/VTAME, VSE/VSAM, CICS/DOS/VS, DOS/VS, Sort/Merge, VSE/ICCF, VSE/OCCF, VSE/IPCS, DOS/COBOL, Back Up/Restore, Space Management, VSE/DITTO), and originally would only agree to offer the individual products separately via [[Request price quotation|RPQ]], although IBM later agreed to add those products individually to its price list under pressure from ISVs who claimed that the bundling violated antitrust laws.<ref>{{Cite journal|last=Blumenthal|first=Marcia|date=15 Mar 1982|title=IBM yields to Adapso heat, unbundles SSX programs|url=https://books.google.com/books?id=Wz-oh7ZQo8MC&pg=PA2|journal=Computerworld|volume=16|issue=11|pages=1–2}}</ref>

===VSE/SP===
In 1986 IBM released '''VSE/SP''' ("System Product") in conjunction with the announcement of the [[IBM 9370|9370]] processors.  VSE/SP replaced SSX/VSE and bundled VSE with the most popular VSE program products such as VSE/AF, [[VTAM#ACF.2FVTAM|ACF/VTAM]], [[CICS]], and [[IBM POWER (software)|POWER/VS]].<ref>{{cite web|last=IBM Corporation|title=IBM VSE/SYSTEM PACKAGE (VSE/SP), VERSION 3 RELEASE 1.1 ENHANCED AND AVAILABLE|date=30 June 1987 |url=http://www-01.ibm.com/common/ssi/cgi-bin/ssialias?subtype=ca&infotype=an&appname=iSource&supplier=897&letternum=ENUS287-332&open&cm_mmc=5733-_-n-_-vrm_newsletter-_-10207_134134&cmibm_em=dm:0:12046832|access-date=June 1, 2011}}</ref> VSE/SP supported only 24-bit addresses, despite customer requests to provide an XA (31 bit) version.

===VSE/ESA===
VSE/ESA was a 31-bit DOS/VSE version, which was released in 1990 with support for up to 384&nbsp;MB of real storage. It provided up to twelve ''static partitions'' and allowed VSE/POWER and ACF/VTAM to be run in ''private address spaces''. It introduced a new feature called ''dynamic partitions'' which could allow up to 150 concurrent jobs, each in its own address space.<ref name=VSEESAAnnounce>{{cite web|last=IBM Corporation|title=IBM VSE/ENTERPRISE SYSTEMS ARCHITECTURE VERSION 1 RELEASE 1|date=5 September 1990 |url=http://www-01.ibm.com/common/ssi/cgi-bin/ssialias?infotype=an&subtype=ca&appname=Demonstration&htmlfid=897/ENUS290-513|access-date=May 31, 2012}}</ref> Version 1 could run in either ESA or 370 mode, with the ESA mode also supporting XA hardware with limitations. Version 2 (1995) only supported ESA mode with ESA hardware. Version 2 added support for [[multiprocessing]], through the new ''Turbo Dispatcher'', which permits different partitions to execute simultaneously on different processors. A partition can only run on one processor at a time, which mostly limits the multiprocessing to [[Computer multitasking|multitasking]]. Up to ten processors are theoretically supported ("tolerated"), but up to four are effectively utilized.<ref>{{cite web |title=VSE/ESA Version 2 Release 1 and VSE/ESA Languages -- PL/I, COBOL, LE Software Announcement | date=13 September 1994 |url=https://www.ibm.com/common/ssi/ShowDoc.wss?docURL=/common/ssi/rep_ca/9/897/ENUS294-519/index.html&lang=en-ZZ-ZZ |publisher=IBM}}</ref><ref>{{cite web |title=VSE/ESA Turbo Dispatcher Guide and Reference |url=https://ibmdocs.pocnet.net/SC33-6797-00.pdf }}</ref> Those limits remain in the last z/VSE.<ref>{{cite web |title=The z/VSE Turbo Dispatcher |url=https://www.ibm.com/docs/en/zvse/6.2?topic=SSB27H_6.2.0/fa2pl_zvse_turbo_dispatcher.htm |publisher=IBM}}</ref>

===z/VSE===
{{main|z/VSE}}
IBM released z/VSE 3.1 in 2005. This change in naming reflected the new "System z" branding for IBM's mainframe product line, but did not represent a fundamental change in architecture from VSE/ESA 2.7 which preceded it. In particular, it did not support the new 64-bit z/Architecture, running only in 31-bit mode even on 64-bit capable machines. z/VSE 4.1 released in 2007 introduced support for 64-bit real addressing, with up to 8&nbsp;GB of memory. However, while parts of the supervisor run in 64-bit mode, it only provides 31-bit virtual address spaces to problem state applications. As of 2011 one estimate placed the number of sites using z/VSE at around 4,000.<ref>{{cite mailing list|url=https://groups.google.com/d/msg/bit.listserv.vse-l/g3fv5ROPc_4/Oc9Y7rGg7zkJ|title=IBM DOS, DOS/VS, DOS/VSE, VSE/SP, VSE/ESA, z/VSE Customers|mailing-list=VSE-L|date=November 2, 2011|access-date=April 25, 2017}}</ref>