User`s guide

The size of the BDOS region differs for the banked and nonbanked versions of
CP/M 3. In the banked version, the resident BDOS size is 6 pages, 1.5K. In the
nonbanked system, the BDOS size ranges from 31 pages, 7.75K, to 33 pages, 8.25K,
depending on system generation options and BIOS requirements.
RSXs are page aligned modules that are stacked in memory below LOADER_base
in memory. In the configuration shown in Figure 1-6, location 0005H of Page Zero
contains a jump to location RSX(N)_base + 6. Thus, the memory ceiling of the TPA
region is reduced when RSXs are active.
Under CP/M 3. the CCP is a transient program that the BIOS loads into the TPA
region of memory at system cold and warm start. The BIOS also loads the LOADER
module at this time, because the LOADER module is attached to the CCP. When the
CCP gains control, it relocates the LOADER module just below BDOS_base. The
LOADER module handles program loading for the CCP. It is three pages long.
The maximum size of a transient program that can be loaded into the TPA Is
limited by LOADER-base because the LOADER cannot load a program over itself.
Transient programs may extend beyond this point, however, by using memory above
LOADER - base for uninitialized data areas such as I/O buffers. Programs that use
memory above BDOS-base cannot make BDOS function calls.
1.5 Disk and Drive Organization and Requirements
CP/M 3 can support up to sixteen logical drives, identified by the letters A through
PI, with up to 512 megabytes of storage each. A logical drive usually corresponds to
a physical drive on the system, particularly for physical drives that support remova-
ble media such as floppy disks. High-capacity hard disks, however, are commonly
divided up into multiple logical drives. Figure 1-7 illustrates the standard organiza-
tion of a CP/M 3 disk.
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1.4 Region Boundaries CP/M 3 Programmer's Guide