Basic Disk Operating System (BDOS) Functions
The "SELECT"
error
is
also issued as the result
of
an
error condition returned to the
BDOS from the BIOS module. The BDOS makes a BIOS disk select call prior to
issuing any
BIOS read
or
write to a particular drive.
If
the selected drive
is
not
supported in the BIOS module, it returns an error code to the BDOS resulting in this
error message.
CP/M-86
terminates the currently running program
and
returns
to
the command level
of
the
CCP
following any input from the console.
The
"R/O"
message occurs when the BDOS receives a command
to
write to a drive
that
is
in
read/only
status. Drives may be placed in
read/only
status explicitly by a
STAT command
or
BDOS function call,
or
implicitly if the BDOS detects
that
a
diskette medium has been changed
and
a warm start has
not
been performed. The
ability to detect changed media
is
optionally included in the BIOS,
and
exists only if
a checksum vector
is
included for the selected drive. When any character
is
pressed
on the keyboard, the transient program
is
aborted
and
control returns
to
the CCP.
RESET DISK SYSTEM
ENTRY
RETURN
CL:
ODH
FUNCTION
13
RESET DISK SYSTEM
The Reset Disk function programmatically restores the file system
to
a reset state
where all drives are set to
read/write
(see functions
28
and
29)
and
Drive A is
selected as the default. This function can be used, for example, by
an
application
program which requires diskette changes during operation. Function
37
(Reset
Drive) can also be used for this purpose.
4-13
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