private byte checkWords() throws IOException
    {
        if (currentSpelling.toString().toUpperCase().equals("ELSE"))
            return Token.ELSE;
        if (currentSpelling.toString().toUpperCase().equals("END"))
            return Token.END;
        if (currentSpelling.toString().toUpperCase().equals("IF"))
            return Token.IF;
        if (currentSpelling.toString().toUpperCase().equals("READ"))
            return Token.READ;
        if (currentSpelling.toString().toUpperCase().equals("REPEAT"))
            return Token.REPEAT;
        if (currentSpelling.toString().toUpperCase().equals("THEN"))
            return Token.THEN;
        if (currentSpelling.toString().toUpperCase().equals("UNTIL"))
            return Token.UNTIL;
        if (currentSpelling.toString().toUpperCase().equals("WRITE"))
            return Token.WRITE;
        if (currentSpelling.toString().toUpperCase().equals("EOT"))
            return Token.EOT;
        else return Token.IDENTIFIER;
    }