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  Interrupt:   21h     Function:   44h     Subfunction:   06h
 
  Title:       IOCTL: Check Input Status
 
  Description:
 
     Returns a code indicating whether the device or file associated
     with a handle is ready for input. This function can be used to
     check the status of character devices such as the serial port
     that do not have their own "traditional" MS-DOS status calls.
 
     Input           Output
 
     AH = 44h        If function successful
     AL = 06h          Carry flag: clear
     BX = Handle     And for a device
                       AL = 00h (if device not ready)
                          = FFh (if device ready)
                     Or for a file
                       AL = 00h (if file pointer at EOF)
                          = FFh (if file pointer not at EOF)
 
                     If function unsuccessful
                       Carry flag: set
                       AX = Error code (01h, 05h, 06h,or 0Dh)
                       See: ◄Error codes►
                                    -♦-