User`s guide

2.3 BDOS File System CP/M 3 Programmer's Guide
Table 2-10. BDOS Physical and Extended Errors
Code Meaning
00 - no error, or not a register H error
01 - Disk I/O error
02 - Read-Only Disk
03 - Read-Only File or File Opened
under user zero from another user
number or file password protected
in write mode and correct pass-
word not specified.
04 - Invalid Drive : drive select error
07 - Password Error
08 - File Exists
09 - ? in Filename
The following two functions represent a special case because they return an address
in registers H and L.
27. Get Addr(Alloc)
31. Get Addr(Disk Parms)
When the BDOS is in return error mode, and it detects a physical error for these
functions, it returns to the calling program with registers A, H, and L all set to 255.
Otherwise, they return no error code.
2.4 Page Zero Initialization
Page Zero is the region of memory located from 0000H to 00FFH. This region
contains several segments of code and data that are used by transient programs while
running under CP/M 3. The code and data areas are shown in Table 2-11 for reference.
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2.3 BDOS File System CP/M 3 Programmer's Guide