Function  22h  Random Write to File Specified by FCB                      (FCB) 
     Writes one record as specified in the Struct -FCB to the current DTA
entry   AH      22h 
	DS:DX	address of the opened Struct -FCB
return  AL      00h     successful write operation 
		01h     disk full; no data written (write was canceled) 
		02h     DTA too small for the record size specified (write was 
			canceled) 
note 1) This service cannot write to read-only files. 
     2) The record pointed to by the Current Block (offset 0Ch) and the Current 
	Record (offset 20h) fields is loaded at the DTA, then the Current Block 
	and Current Record fields are incremented. 
     3) If the record size is less than a sector, the data in the DTA is written 
	to a buffer; the buffer is written to disk when it contains a full  
	sector of data, the file is closed, or a Reset Disk (function 0Dh) is 
	issued. 
     4) The current file pointers are NOT incremented this function. 
     5) The record is written to disk at the current DTA address as specified  
	by the most recent call to function 1Ah. If the size of the record and 
	location of the DTA are such that a segment overflow or wraparound would 
	occur, the error return is set to AL=02h