Editing Transaction Processing Facility (section)

====Memory usage====
Historically and in step with the previous, core blocks— memory— were also 381, 1055 and 4&nbsp;K bytes in size. Since '''ALL''' memory blocks had to be of this size, most of the overhead for obtaining memory found in other systems was discarded. The programmer merely needed to decide what size block would fit the need and ask for it. TPF would maintain a list of blocks in use and simply hand out the first block on the available list.

Physical memory was divided into sections reserved for each size so a 1055 byte block always came from a section and returned there, the only overhead needed was to add its address to the 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&nbsp;KB in size (1&nbsp;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.