MODULE BinaryDigits;
IMPORT  Out;

  PROCEDURE OutBin(x: INTEGER);
  BEGIN
    IF x > 1 THEN OutBin(x DIV 2) END;
    Out.Int(x MOD 2, 1);
  END OutBin;


BEGIN
  OutBin(0); Out.Ln;
  OutBin(1); Out.Ln;
  OutBin(2); Out.Ln;
  OutBin(3); Out.Ln;
  OutBin(42); Out.Ln;
END BinaryDigits.