Early generation (1950s) mainframe does not have an operating system. It run batch one at a time. Operator will feed the program to card reader together with the subroutine deck the program uses. Operator also allocate the devices required. When the program ends, operator deallocate the device es and prepare for the next step (program) to run. The operation is manual.
The first rudimentary OS at early 1960d are Primary Control Program (PCP) and Disk Operation System (DOS). These OS mechanizing job transition. Device allocation is still Manual. The OS will search for the subroutine library to retrieve the program requires to run. The system is still running one job at a time.
MFT (multi programming with fixed number or task) came out in 1967 for OS/360. It support running a fixed number of jobs co currently. JCL is used to separate the program from operations (device, dispatching etc). Output is managed by HASP. Multi programming led to TSO and RJE.
MFT gave rise to MVT (variable number of task). More programming language is supported include PL/1, ALGOL, APL and Basic.
In 973, three new OS came out - SVS，VS and VM370 all supporting virtual storage. This eliminate the overlay technics. As demand to support more users gave birth to MVS in 1974
The evolution of mainframe OS improved productivity of users and application and system programmers. It automate computer operations, workload management, data and resource management.
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