Function  0Eh   Select Disk 
      Sets the drive specified in DL (if valid) as the default drive 
entry   AL      0Eh 
	DL      new default drive number (0=A:,1=B:,2=C:,etc.) 
return  AL      total number of logical drives (not nescessarily physical) 
note 1) For DOS 1.x and 2.x, the minimum value for AL is 2. 
     2) For DOS 3.x and 4.x, the minimum value for AL is 5. 
     3) The drive number returned is not nescessarily a valid drive. 
     4) For DOS 1.x: 16 logical drives are availible, A-P. 
	For DOS 2.x: 63 logical drives are availible. (Letters are only used for 
		     the first 26 drives. If more than 26 logical drives are 
		     used, further drive letters will be other ASCII characters 
		     ie \{,], etc. 
	For DOS 3.x: 26 logical drives are availible, A-Z. 
	For DOS 4.x: 26 logical drives are availible, A-Z.