User`s guide

Upon return, Function 35 returns a zero in register A if the file specified by the
referenced FCB is found, or an OFFH in register A if the file is not found. Register H
is set to zero in both of these cases. If a physical error is encountered, Function 35
performs different actions depending on the BDOS error mode (see Function 45).
If the BDOS error mode is the default mode, a message identifying the error is
displayed at the console and the program is terminated. Otherwise, Function 35
returns to the calling program with register A set to OFFH, and register H set to one
of the following physical errors:
01 Disk I/O error
04 Invalid drive error
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BDOS Function Calls CP/M 3 Programmers Guide