User`s guide

The default DMA address for transient programs is 0080H. The CCP also initial-
izes this area to contain the command tall of the command line. The first position
contains the number of characters in the command line, followed by the command
line characters. The character following the last command tail character is set to
binary zero. The command line characters are preceded by a leading blank and are
translated to ASCII upper-case. Because the 128-byte region beginning at 0080H is
the default DMAI, the BDOS file system moves 128-byte records to this area with
read operations and accesses 128-byte records from this area with write operations.
The transient program must extract the command tail information from this buffer
before performing file operations unless it explicitly changes the DMA address with
the BDOS Set DMA Address function.
The Page Zero fields of 0051H through OOS6H locate the password fields of the
first two file specifications in the command tail if they exist. These fields are provided
so that transient programs are not required to parse the command tail for password
fields. However, the transient program must save the password, or change the DMA
address before performing file operations.
The following example illustrates the initialization of the command line fields of
Page Zero. Assuming the following command line is typed at the console:
D>A:PROGRAM B:FILE,TYPE ; PASS C ;FILE.TYPE ; PASSWORD
A hexadecimal dump of 0050H to 0OA5H would show the Page Zero initialization
performed by the CCP.
005OH: 01 0D 00 04 9D 00 08 00 00 00 00 00 02 46 49 4C . . . . . . . . . . . . . . .FIL
006OH: 45 20 20 20 20 54 59 50 00 00 00 00 03 46 49 4C E . . . . TYP . . . . . FIL
007OH: 45 20 20 20 20 54 59 50 00 00 00 00 00 00 00 00 E . . . . TYP . . . . . . . .
0050H: 24 20 42 3A 46 49 4C 45 2E 54 59 50 3B 50 41 53 . . B:FILE.TYP;PAS
009OH: 53 20 43 3A 46 49 4C 45 2E 54 59 50 3B 50 41 53 S C:FILE.TYP;PAS
OOAOH: 53 57 4F 52 44 00 SWORD.
End of Section 2
2-38
2.4 Page Zero Initialization CP/M 3 Programmer's Guide