The IBM operating system MVS was the most commonly used on the System/370 and System/390 mainframes.
It's acronym stands for Multiple Virtual Storage. It was a logical progression from MFT which ran
jobs in predefined partition sizes. The version 3.8J is the last version that was made available
to the public free of charge and can be run on a PC without license issues. The major restriction
of this version is it is limited to 16Mb main memory to be split among all tasks. Later licensed
versions of this OS used 31 bit addressing instead of 24 bit. This operating system was designed
primarily for batch processing of large amounts of customer billing and account information. It would
not be unusual for a small shop to process and print 30,000 customer bills a night every week night.
MVS does include TSO (Time Sharing Option) which was an early development in making computers
interactive and responsive to transactions as they happen.