INT E0 - DR Multiuser DOS - "A_READ" - READ CHARACTER FROM AUX DEVICE
        CL = 03h
Return: AL = ASCII character
Notes:  A_READ reads the next 8-bit character from the logical auxilliary
          input device (AUXn:); control is not returned to the calling
          process until a character has been read.
        if another process owns AUX, this call blocks until the device becomes
          available
SeeAlso: INT E0/CL=04h,INT E0/CL=07h,INT E0/CL=A5h,INT E0/CL=ACh