PURPOSE: A printer so constructed that a printer of the standard specifications can be easily modified into various kinds of printers, wherein blank cover for an input part and an indicating part can be replaced with each other, and a printer can be modified into one for different purpose by replacing an ROM with a blank cover.

CONSTITUTION: Hardware of the printer is so constructed that it can be adapted to various kinds of printers for different purposes, and the blank cover for the input part 2a for setting printing items and the indicating part 2b for indicating the printing items can be replaced with each other. By replacing the ROM9 (which stores controlling programs for the printer) with the blank cover 2', the printer can be modified into various kinds of printers such as a journal printer or a label printer.