Source : Free On-Line Dictionary of Computing

Transaction Processing Facility
     
         (TPF) A {real-time} {mainframe} {operating
        system} released by {IBM} around 1976.  TPF is particularly
        suited to organisations dealing in very high I/O message
        switching and large global networks.  Current users include
        British Airways (reservations), VISA International
        (authorisations), Holiday Inn, and Quantas.
     
        TPF was traditionally a {370/Assembler} environment although
        the latest, release 4.1, contains {C}.  Formerly known as ACP
        (Airline Control Program), it was renamed "TPF" to suggests
        its greater scope.
     
        It is common for TPF sites to use IBM's {MVS} and {VM}
        operating systems for {off-line} processing.
     
        (1996-08-27)