PROGRAM Binary;
USES Crt; {<== Comment out this line for TP3}
{ This program displays a binary number from 0 to 7
  using the Caps/Num/Scroll Lock LED indicators. }

TYPE  LEDnum = 0..7;
VAR   B : Byte;
      dummy : char;

  PROCEDURE BinLed(L : LEDnum);
  VAR ShiftByte : byte absolute $0000:$0417;
     { shift status byte }
  BEGIN
    ShiftByte := L SHL 4;
  END;

BEGIN
  WriteLn('Press a key to display binary numbers on the LEDs.');
  WriteLn('Press another key to stop the display.');
  dummy := ReadKey;  {<== comment out this line for TP3}
  {Read(Kbd,dummy);} {<== UN-comment this line for TP3}
  B := 0;
  REPEAT
    WriteLn('Displaying ',B);
    BinLed(B);
    Delay(1000);
    B := Succ(B) MOD 8;
  UNTIL KeyPressed;
  BinLed(0); {Turn off shift states!}
END. { PROGRAM Binary }