function dtypeChar( dtype ) {
	if ( arguments.length === 0 ) {
		return table();
	}
	if ( TABLE === void 0 ) {
		TABLE = table();
	}
	return TABLE[ resolve( dtype ) ] || null;
}
Returns the single letter character abbreviation for an underlying array data type.

@param {*} [dtype] - data type value
@returns {(Object|string|null)} single letter character abbreviation(s)

@example
var obj = dtypeChar();
// returns {...}

@example
var ch = dtypeChar( 'float64' );
// returns 'd'

ch = dtypeChar( 'generic' );
// returns 'o'