Source : Free On-Line Dictionary of Computing

Operating System/Multiprogramming of Fixed Tasks
     
         (OS/MFT) One of the {IBM} {operating
        systems} associated with the {IBM 360}, released in 1966 and
        targetted at mid-range {IBM 360} users (typically 360/40,
        360/50).  OS/MFT was the juinior member of the main 'OS'
        series of IBM operating systems, the other being {OS/MVT}.
        Smaller 360 mainframes used {DOS}.
     
        OS/MFT shared {JCL} and utilities with OS/MVT but allocated
        memory differently.  In OS/MFT, partitions of memory were of a
        fixed number and size, specified by the generation and
        configuration of the operating system.  As this class of
        mainframe had typically less than 512K of main memory,
        partitions tended to be about 128K.
     
        With the advent of {Virtual Storage} and the {System 370}'s
        {Dynamic Address Translation} (DAT), OS/MFT was improved to
        become {OS/VS1}, taking account of virtual storage in a single
        partition up to 16MB.
     
        (1999-01-22)