WHILE NOT EOLN (INPUT) DO
        BEGIN
        READ (x);
        IF NOT (x IN ['A'..'Z', 'a'..'z', '0'..'9'])
        THEN
           Err := Err + 1;
        END;

  This example reads an input character (x) from the current line.
  If  the  character  is  not  a digit or letter, the error count,
  'Err', is incremented by  one.   The  loop  terminates  when  an
  end-of-line on the INPUT is reached.