The carriage (12) is displaced by a toothed belt (33) which is driven continuously by an electric motor (48) and is connected to the carriage by means of a drive element (32) engaged between two teeth of the belt and slidable on bars (27) on the carriage in a direction perpendicular to the direction of displacement of the carriage. The pulleys are provided with recesses (42, 43) capable of engaging the drive element in such a way as to move it positively in the perpendicular direction as it moves round a pulley. The carriage is also connected by means of a tension spring (58) to a strip (52) provided with indicia of an optical encoder, sensed by an optical reader (57). The upper paper pressure arrangement is formed by two rollers (85) carried by two sliders (83) fitted into corresponding longitudinal slots in the fixed support. The paper is carried by a feed reel which is carried by two arms (94) which can be fitted by catch engagement on corresponding shoulders on the fixed support. The printer is particularly suitable for being connected to the output of a personal or home computer.