function Byte2hex(D:char):word;
asm
  mov  AH,AL
  and  AL,0Fh
  add  AL,90h
  daa
  adc  AL,40h
  daa
  xchg AL,AH
  shr  AL,4
  add  AL,90h
  daa
  adc  AL,40h
  daa
end;