Editing CP/M (section)

=== Transient Program Area ===

The read/write memory between address 0100 hexadecimal and the lowest address of the BDOS was the ''Transient Program Area'' (TPA) available for CP/M application programs. Although all Z80 and 8080 processors could address 64 kilobytes of memory, the amount available for application programs could vary, depending on the design of the particular computer. Some computers used large parts of the address space for such things as BIOS ROMs, or video display memory. As a result, some systems had more TPA memory available than others. Bank switching was a common technique that allowed systems to have a large TPA while switching out ROM or video memory space as needed. CP/M&nbsp;3.0 allowed parts of the BDOS to be in bank-switched memory as well.