INT 21 - DOS 1+ - PARSE FILENAME INTO FCB
AH = 29h
AL = parsing options
bit 0: skip leading separators
bit 1: use existing drive number in FCB if no drive is specified,
instead of setting field to zero
bit 2: use existing filename in FCB if no base name is specified,
instead of filling field with blanks
bit 3: use existing extension in FCB if no extension is specified,
instead of filling field with blanks
bits 4-7: reserved (0)
DS:SI -> filename string (both '*' and '?' wildcards OK)
ES:DI -> buffer for unopened FCB
Return: AL = result code
00h successful parse, no wildcards encountered
01h successful parse, wildcards present
FFh failed (invalid drive specifier)
DS:SI -> first unparsed character
ES:DI buffer filled with unopened FCB (see AH=0Fh)
Notes:  asterisks expanded to question marks in the FCB
all processing stops when a filename terminator is encountered
cannot be used with filespecs which include a path (DOS 2+)
SeeAlso: AH=16h,AH=26h

See also: 210F

2129 - DOS 1+ - PARSE FILENAME INTO FCB