Function  29h  Parse the Command Line for Filename 
     Parses a text string into the fields of a File Control Block Struct -FCB
entry   AH      29h 
	DS:SI   pointer to string to parse 
	ES:DI	pointer to memory buffer to fill with unopened Struct -FCB
	AL      bit mask to control parsing 
		bit 0 = 0: parsing stops if file seperator found 
                        1: causes service to scan past leading chars such as 
			   blanks. Otherwise assumes the filename begins in the
			   first byte
		    1 = 0: drive number in Struct -FCB set to default (0) if
			   string contains no drive number
                        1: drive number in Struct -FCB not changed
		    2 = 0: filename in Struct -FCB set to 8 blanks if no
			   filename in string
			1: filename in Struct -FCB not changed if string does
			   not contain a filename
		    3 = 0: extension in Struct -FCB set to 3 blanks if no
			   extension in string
                        1: extension left unchanged 
                    4-7    must be zero 
return  AL      00h     no wildcards in name or extension 
		01h     wildcards appeared in name or extension 
		0FFh    invalid drive specifier 
	DS:SI   pointer to the first byte after the parsed string 
	ES:DI	pointer to a buffer filled with the unopened Struct -FCB
note 1) If the * wildcard characters are found in the command line, this
	service will replace all subsequent chars in the Struct -FCB with
	question marks.
     2) This service uses the characters as filename separators 
	DOS 1       : ; . , + / [ ] = " TAB SPACE 
	DOS 2,3     : ; . , + = TAB SPACE 
     3) This service uses the characters 
	: ; . , +   | / \\ [ ] = " TAB SPACE 
	or any control characters as valid filename separators 
     4) A filename cannot contain a filename terminator. If one is encountered, 
	all processing stops. The handle functions will allow use of some of 
	these characters. 
     5) If no valid filename was found on the command line, ES:DI +1 points 
	to a blank (ASCII 32). 
     6) This function cannot be used with filespecs which include a path 
     7) Parsing is in the form D:FILENAME.EXT. If one is found, a corresponding 
	unopened Struct -FCB is built at ES:DI
 


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