User`s guide

BDOS directory functions operate on existing file entries in a drive's directory.
This category includes functions to search for one or more files, delete one or more
files, truncate a file, rename a file, set file attributes, assign a password to a file, and
compute the size of a file. The search and delete functions are the only BDOS func-
tions that support ambiguous file references. All other directory and fi e related func-
tions require a specific file reference.
The BDOS drive-related category includes functions that select the default drive,
compute a drive's free space, interrogate drive status, and assign a directory label to
a drive. A drive's directory label controls whether or not CP/M 3 enforces file pass-
word protection, or stamps files with the date and time. Note that the nonbanked
version of CP/M 3 does not support file passwords.
The miscellaneous category includes functions to set the current DMA address,
access and update the current user number, chain to a new program, and flush
internal blocking/deblocking buffers. Also included are functions that set the BDOS
multi-sector count, and the BDOS error mode. The BDOS multi-sector count deter-
mines the number of 128-byte records to be processed by BDOS read and write
functions. It can range from 1 to 128. The BDOS error mode determines how the
BDOS file system handles certain classes of errors.
Also included in the miscellaneous category are functions that call the BIOS directly,
set a program return code, and parse filenames. If the LOADER RSX is resident in
memory, programs can also make a BDOS function call to load an overlay. Another
miscellaneous function accesses system variables in the System Control Block.
2-8Pb
The following list summarizes the operations performed by the BDOS file system-
2.3 BDOS File System CP/M 3 Programmer's Guide