Function  0Dh   Disk Reset 
      Flushes all currently open file buffers to disk 
entry   AH      0Dh 
return          none 
note 1) Does not close files. Does not update directory entries; files changed 
	in size but not closed are not properly recorded in the directory 
     2) Sets DTA address to DS:0080h 
     3) Should be used before a disk change, Ctrl-C handlers, and to flush 
	the buffers to disk.