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Basic Disk Operating System (BDOS) Functions
4-16
An ASCII question mark (3FH) in any position from "fl" through "ex" matches the
corresponding field of any directory entry on the default or auto-selected disk drive.
If the "dr" field contains an ASCII question mark, then the auto disk select function
is disabled, the default disk is searched, and the search function returns any
matched entry, allocated or free, belonging to any user number. This latter function
is not normally used by application programs, but does allow complete flexibility to
scan all current directory values. If the "dr" field is not a question mark, the "s2" byte
is automatically zeroed.
SEARCH FOR NEXT
ENTRY
CL: 12H
FUNCTION 18
SEARCH FOR NEXT
RETURN
AL: Function
Code
The Search for Next function is similar to the Search for First function, except that
the directory scan continues from the last matched entry. Function 18 returns the
value OFFH in AL when no more directory items match, and any other value when a
match is found. In terms of execution sequence, a Search for Next call must follow
either a Search for First or Search for Next call with no other intervening BDOS
disk-related function calls.
DELETE FILE
ENTRY
CL: 13H
DX: FCB
Offset
RETURN
FUNCTION
19
AL: Return Code
DELETE FILE
The Delete File function removes files which match the FCB addressed by DX. The
file name and type may contain ambiguous references (i.e, question marks in
various positions), but the drive select code cannot be ambiguous, as in the Search
for First and Search for Next functions. Function 19 returns OFFH (255 decimal) if
the referenced file or files cannot be found. Otherwise, it returns zero.
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