A computer that does not have a fixed word length but operates on data of different word lengths; this may also apply to instruction sizes. The lengths of data words that can be handled are usually in units of characters or bytes, so that the computer handles strings of characters or bytes. It is then known as a character machine or byte machine respectively. Variable word length computers were once considered particularly important where data are themselves of varying lengths (e.g. strings of characters) or where natural data lengths do not fit word (hardware-restricted) boundaries. However, the cost of such special-purpose hardware is no longer justified, given the very high processing speeds of modern general-purpose fixed word length computers.