Editing IBM System/360 (section)

===Operating system software===
{{Main|History of IBM mainframe operating systems#System/360 operating systems|l1=System/360 operating systems}}

The smaller System/360 models used the Basic Operating System/360 ([[BOS/360]]), Tape Operating System (TOS/360), or Disk Operating System/360 ([[DOS/360]], which evolved into DOS/VS, DOS/VSE, VSE/AF, VSE/SP, VSE/ESA, and then [[VSE (operating system)|z/VSE]]).

The larger models used [[OS/360 and successors|Operating System/360]] (OS/360). IBM developed several levels of OS/360, with increasingly powerful features: Primary Control Program (PCP), [[MFT (operating system)|Multiprogramming with a Fixed number of Tasks]] (MFT), and [[Multiprogramming with a Variable number of Tasks]] (MVT). MVT took a long time to develop into a usable system, and the less ambitious MFT was widely used. PCP was used on intermediate machines too small to run MFT well, and on larger machines before MFT was available; the final releases of OS/360 included only MFT and MVT.  For the [[System/370]] and later machines, MFT evolved into [[OS/VS1]], while MVT evolved into [[OS/VS2 (SVS)]] (Single Virtual Storage), then various versions of [[MVS]] (Multiple Virtual Storage) culminating in the current [[z/OS]].

When it announced the [[IBM System/360 Model 67|Model 67]] in August 1965, IBM also announced [[TSS/360]] (Time-Sharing System) for delivery at the same time as the 67. TSS/360, a response to [[Multics]], was an ambitious project that included many advanced features. It had performance problems, was delayed, canceled, reinstated, and finally canceled<ref group=NB>However, it could still be ordered, and a TSS/370 [[Request price quotation|PRPQ]] was available on the S/370 and went through multiple releases.</ref> again in 1971. Customers migrated to [[CP-67]], MTS ([[Michigan Terminal System]]), TSO ([[Time Sharing Option]] for OS/360), or one of several other [[time-sharing]] systems.

CP-67, the original [[virtual machine]] system, was also known as [[CP/CMS]]. CP/67 was developed outside the IBM mainstream at IBM's [[Cambridge Scientific Center]], in cooperation with [[MIT]] researchers. CP/CMS eventually won wide acceptance, and led to the development of [[VM/370]] (Virtual Machine) which had a primary interactive "sub" operating system known as [[VM/CMS]] (Conversational Monitoring System). This evolved into today's [[z/VM]].

The Model 20 offered a simplified and rarely used tape-based system called TPS (Tape Processing System), and DPS (Disk Processing System) that provided support for the 2311 disk drive. TPS could run on a machine with 8&nbsp;KB of memory; DPS required 12&nbsp;KB, which was pretty hefty for a Model 20. Many customers ran quite happily with 4&nbsp;KB and CPS (Card Processing System). With TPS and DPS, the card reader was used to read the [[Job Control Language]] cards that defined the stack of jobs to run and to read in transaction data such as customer payments. The operating system was held on tape or disk, and results could also be stored on the tapes or hard drives. Stacked job processing became an exciting possibility for the small but adventurous computer user.

A little-known and little-used suite of 80-column punched-card utility programs known as [[IBM Basic Programming Support|Basic Programming Support]] (BPS) (jocularly: Barely Programming Support), a precursor of TOS, was available for smaller systems.