A printer for printing characters through a printing ribbon on printing paper placed on a platen by moving a carriage along the platen and driving a printing head on the carriage. The platen is placed in the rear end portion of the printer frame. An opening for insertion of printing paper is formed in the rear end surface of the frame to which the platen is approximated. Various paper feeders for automatically supplying single sheets or a continuous printing paper are connected to the rear of the printer frame so as to face the open area. A feed roller is moved against the platen when a paper feeder is installed.