User`s guide

The CCP initializes Page Zero prior to initiating a transient program. The fields at

0050H and above are initialized from the command line invoking the transient pro-

gram. The command line format was described in detail in Section 1.6.2. To sum-

marize, a command line usually takes the form:

where

<command tail> = > (no command tail)

= > <file Spec>

= > <file spec><delimiter><file spec>

<file spec> = > {d:}filename{.type} {;password}

The CCP initializes the command drive field at 0050H to the drive index, A = 1,

P = 16, of the drive from which the transient program was loaded.

The default FCB at 005CH is defined if a command tail is entered. Otherwise, the

fields at 005CH, 0068H to 006BH are set to binary zeros, the fields from 005DH to

0067H are set to blanks. The fields at 0051H through 0053H are set if a password

is specified for the first <file Spec> of the command tail. If not, these fields are set to

zero.

The default FCB at 006CH is defined if a second <file spec> exists in the com-

mand tail. Otherwise, the fields at 006CH, 0078H to 007BH are set to binary zeros,

the fields from 005DH to 0067H are set to blanks. The fields at 0054H through

0056H are set if a password is specified for the second <file spec> of the command

tail. If not, these fields are set to zero.

Transient programs often use the default FCB at 005CH for file operations. This

FCB may even be used for random file access because the three bytes starting at

007DH are available for this purpose. However, a transient program must copy the

contents of the default FCB at 006CH to another area before using the default FCB

at 005CH, because an open operation for the default FCB at 005CH overwrites the

FCB data at 006CH.

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2.4 Page Zero Initialization CP/M 3 Programmer's Guide