Listing:

    1  MODULE RPtr;
    2  VAR ExitCode : INTEGER;
    3      p, q : POINTER TO INTEGER;
    4  BEGIN
    5    ExitCode := 0;
    6    p := NIL;
    7    q := p;
    8    IF p = NIL THEN ExitCode := ExitCode + 1 END;
    9    IF q = NIL THEN ExitCode := ExitCode + 10 END;
   10    IF p = q THEN ExitCode := ExitCode + 100 END
   11  END RPtr.

    0 errors