PURPOSE: To make possible the setting of a printer when an ink ribbon with different properties is used by providing an uneven surface or a light reflective piece on an ink ribbon cassette.

CONSTITUTION: An ink ribbon cassette consists of a winding part 1, a supply part 2, a frame part 3 and an ink ribbon 4. A projecting part or a recessed part is formed on a part of the frame part, and the ink ribbon cassette is introduced from an arrow direction and the recessed part 5 is engaged with a push switch 10 provided on a frame 11 for a printer. Then the printing format of this printer is controlled in accordance with the switching of the push switch 10. In addition, an optical reflective switch is used instead of the push switch, on a printer side, if the ink ribbon cassette has a light reflective piece, for example, a metal piece attached in lieu of an uneven surface provided.