User`s guide

Table 2-11. Page Zero Areas
Location Contents
From TO
0000H - 0002H Contains a jump instruction to the BIOS warm start entry
point at BIOS - base + 3. The address at location OOOIH can
also be used to make direct BIOS calls to the BIOS console
status, console input, console output, and list output primitive
functions.
0003H - 0004H (Reserved)
0005H - 0007H Contains a jump instruction to the BDOS, the LOADER, or
to the most recently added RSX, and serves two purposes:
JMP 0005H provides the primary entry point to the BDOS,
and LHLD 0006H places the address field of the jump
instruction in the HL register pair. This value, minus one, is
the highest address of memory available to the transient
program.
0008H - 003AH Reserved interrupt locations for Restarts 1 - 7
003BH - 004FH (Not currently used - reserved)
0050H Identifies the drive from which the transient program was load-
ed. A value of one to sixteen identifies drives A through P.
0051H - 0052H Contains the address of the password field of the first command-
tail operand in the default DMA buffer beginning at 0080H.
The CCP sets this field to zero if no password for the first
command-tail operand is specified.
0053H Contains the length of the password field for the first command-
tail operand. The CCP also sets this field to zero if no password
for the first command tail is specified.
0054H - 0055H Contains the address of the password field of the second corn-
mand-tail operand in the default DMA buffer beginning at
0080H. The CCP sets this field to zero if no password for the
second command-tail operand is specified.
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2.4 Page Zero Initialization CP/M 3 Programmer's Guide