appropriate physical block table's list. No compaction or data collection was required. As applications got more advanced demands for memory increased, and once C became available memory chunks of indeterminate or large size were required. This gave rise to the use of heap storage and some memory management routines. To ease the overhead, TPF memory was broken into frames— 4 KB in size (1 MB with z/TPF). If an application needs a certain number of bytes, the number of contiguous frames required to fill that need are granted. References Bibliography Transaction Processing Facility: A Guide for Application Programmers (Yourdon Press Computing Series) by R. Jason Martin (Hardcover - April 1990), External links z/TPF (IBM) TPF User Group (TPF User Group) Real-time operating systems IBM mainframe operating systems Transaction processing facility