User`s guide

The BDOS Error Mode, which can exist in three states, determines how the file
system handles physical and extended errors. In the default state, the BDOS displays
the error message, and terminates the calling program, method 2. In return error
mode, the BDOS returns control to the calling program with the error identified in
registers A, H, and L, method 1. In return and display mode, the BDOS returns
control to the calling program with the error identified in registers A, H, and L, and
also displays the error message at the console, method 3. While both return modes
protect a program from termination because of a physical or extended error, the
return and display mode also allows the calling program to take advantage of the
built-in error reporting of the BDOS file system. Physical and extended errors are
displayed on the console in the following format:
CP/M Error on d: error message
BDOS function = nn File = filename.typ
where d identifies the drive selected when the error condition is detected; error mes-
sage identifies the error; nn is the BDOS function number, and filename.typ identifies
the file specified by the BDOS function. If the BDOS function did not involve an
FCB, the file information is omitted. Note that the second line of the above error
message is displayed only in the banked version of CP/M 3 if expanded error message
reporting is requested in GENCPM. It is not displayed in the nonbanked version of
CP/M 3.
The BDOS physical errors are identified by the following error messages:
o Disk I/O
o Invalid Drive
o Read-Only File
o Read-Only Disk
The Disk I/O error results from an error condition returned to the BDOS from the
BIOS module. The file system makes BIOS read and write calls to execute file-related
BDOS calls. If the BIOS read or write routine detects an error, it returns an error
code to the BDOS resulting in this error.
The Invalid Drive error also results from an error condition returned to the BDOS
from the BIOS module. The BDOS makes a BIOS Select Disk call prior to accessing
a drive to perform a requested BDOS function. If the BIOS does not support the
selected disk, the BDOS returns an error code resulting in this error message.
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2.3 BDOS File System CP/M 3 Programmer's Guide