Editing DOS/360 and successors (section)

===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.