Abstract: A read-only memory has a terminal for receiving a writing current and a data input/output terminal. In the writing operation, the writing current is supplied to the terminal which is different from the data input/output terminal. Therefore, a data output circuit can be constituted by an ECL circuit having a relatively low withstand voltage, and a selection circuit related to the reading operation is achieved by using an ECL circuit. Accordingly, the read-only memory performs the reading operation at high speeds. During the writing operation, a different selection circuit is used which can withstand high voltages.