What is an operating system (OS)?

MVS, which stands for Multiple Virtual Storage, is one of the oldest operating systems developed by IBM and distant relative of what we nowadays call DOS. MVS has its own programming language, JCL (Job Control Language). Three decades after MVS was created (1974), JCL is still heavily used. As a matter of fact, where I work, some programmers still use JCL on a daily basis in the IBM z/VM system. Some of the applications where I work query VSAM files and third-party application handle screen scraping to replicate the screens and output to ASP or JSP. After over forty years, the mainframes are still king.

The following table shows the history of MVS as per the book Understanding Operating Systems (ISBN 9780534503536) by Ida Flynn.

Timeline:

  • OS/360 for IBM 360 (1964)
  • OS/MFT (Multiprogramming with Fixed number Tasks) for IBM 360 (1967)
  • OS/MVT (Multiprogramming with Variable number Tasks) for IBM 360 (1968)
  • SVS (Single Virtual Storage)
    OS/VS1 (Virtual Storage 1)
    OS/VS2 (Virtual Storage 2) for IBM 370 (1972)
  • MVS (Multiple VirtualStorage) for IBM 370 (1974)
  • MVS/XA (MVS with Extended Architecture) for IBM 370 (1981)
  • MVS/ESA (MVS with Enterprise System Architecture) for IBM 370 (1985)
  • MVS/ESA (MVS with Enterprise System Architecture for IBM 390 (1990)
  • OS/390 (Open Server 390) for IBM 390 (1996)
  • z/OS 64-bit for zSeries (2000)
  • IBM z/VM for zSeries (2004)

If you want to play with VMS, you can run OpenVMS by VMS Software via the FreeAXP Alpha emulator on Windows by Migration Specialties. There is also a x86 port.