A printer includes a carriage supporting a print head and movable across print paper for enabling the print head to print on the print paper, a fixed frame, a switch device mounted on one of the carriage and the fixed frame, the switch device being composed of a light transmission means and a light blocking means for blocking light passing through the light transmission means, a sensor means on the other of the carriage and the fixed frame for sensing light passing through the switch device to produce an electric signal, and a means for reading the electric signal as information indicative of printer functions in response to movement of the carriage.