Function  11h   Search For First Matching Entry                           (FCB) 
      Searches current disk & directory for first matching filename 
entry   AH      11h 
	DS:DX   pointer to address of FCB 
return  AL      00h     successful match 
		0FFh    no matching filename found 
note 1) The FCB may contain the wildcard character ? under Dos 2.x, and ? or *  
	under 3.x and 4.x. 
     2) The original FCB at DS:DX contains information to continue the search 
	with function 12h, and should not be modified. 
     3) If a matching filename is found, AL returns 00h and the locations at the 
	Disk Transfer Address are set as follows: 
	a) If the FCB provided for searching was an extended FCB, then the first 
	   byte at the disk transfer address is set to 0FFh followed by 5 bytes 
	   of zeroes, then the attribute byte from the search FCB, then the  
	   drive number used (1=A, 2=B, etc) then the 32 bytes of the directory 
	   entry. Thus, the disk transfer address contains a valid unopened FCB 
	   with the same search attributes as the search FCB. 
	b) If the FCB provided for searching was a standard FCB, then the first  
	   byte is set to the drive number used (1=A,2=b,etc), and the next 32  
	   bytes contain the matching directory entry. Thus, the disk transfer  
	   address contains a valid unopened normal FCB. 
     4) If an extended FCB is used, the following search pattern is used: 
	a) If the FCB attribute byte is zero, only normal file entries are  
	   found. Entries for volume label, subdirectories, hidden or system  
	   files, are not returned. 
	b) If the attribute byte is set for hidden or system files, or  
	   subdirectory entries, it is to be considered as an inclusive search. 
	   All normal file entries plus all entries matching the specified  
	   attributes are returned. To look at all directory entries except the 
	   volume label, the attribute byte may be set to hidden + system +  
	   directory (all 3 bits on). 
	c) If the attribute field is set for the volume label, it is considered 
	   an exclusive search, and ONLY the volume label entry is returned. 
     5) This call is also used by the APPEND command in DOS 3.2+