User`s guide

If the Set BDOS Error Mode function is used to place the BDOS in return error
mode, the following functions return an Error Flag on physical errors:
14. Select Disk
46. Get Disk Free Space
48. Flush Buffers
98. Free Blocks
101. Return Directory Label Data
The Error Flag definition for register A is shown in Table 2-9.
Table 2-9. BDOS Error Flags
Code I Meaning
00 successful function
255 physical error : refer to register H
The BDOS returns nonzero values in register H to identify a physical or extended
error if the BDOS Error Mode is in one of the return modes. Except for functions
that return a Directory Code, register A equal to 255 indicates that register H iden-
tifies the physical or extended error. For functions that return a Directory Code, if
register A equals 255, and register H is not equal to zero, register H identifies the
physical or extended error. Table 2-10 shows the physical and extended error codes
returned in register H.
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2.3 BDOS File System CP/M 3 Programmer's Guide