Function  0Bh   Check Standard Input (STDIN) status 
      Checks for character availible at STDIN  
entry   AH      0Bh 
return  AL      0FFh    if a character is availible from STDIN 
		00h     if no character is availible from STDIN 
note 1) Checks for Ctrl-C. If Ctrl-C is detected, int 23h is executed 
     2) Input can be redirected. 
     3) Checks for character only, it is not read into the application 
     4) IBM reports that this call does not work properly under the DOSSHELL 
	program in DOS 4.00 and 4.01. DOSSHELL will return all zeroes. This 
	function works correctly from the command line or application.