function isLetter (c) {
	return ( ((c >= "a") && (c <= "z")) || ((c >= "A") && (c <= "Z")) || c == " " );
}


function isDigit (c) {
	return ((c >= "0") && (c <= "9"));
}

function isLetterOrDigit (c) {
	return (isLetter(c) || isDigit(c));
}