PROCEDURE WRITE_HEX(VAR DEVICE : TEXT; BT : BYTE);

CONST HEXDIGITS : ARRAY[0..15] OF CHAR = '0123456789ABCDEF';

VAR BZ : BYTE;

BEGIN
  BZ := BT AND $0F;
  BT := BT SHR 4;
  WRITE(DEVICE,HEXDIGITS[BT],HEXDIGITS[BZ])
END;