INT 21 - DOS 2+ - IOCTL - GET INPUT STATUS
AX = 4406h
BX = file handle
Return: CF clear if successful
AL = input status
00h not ready (device) or at EOF (file)
FFh ready
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:   files may not register as being at EOF if positioned there by AH=42h
SeeAlso: INT 2F/AX=122Bh

See also: 214407

214406 - DOS 2+ - IOCTL - GET INPUT STATUS