Abstract: When format information is changed, print area check data is generated as per the changed format information (S25). If the check data is found not to be printable within the print area of the tape defined by the printable width and set tape length ("YES" in S27), the changed format information is invalidated (S28), and a message indicating what has taken place appears on the display (S29). Whenever a character or the like is input, the corresponding print check data is generated (S33). If the data is found to be printable within the print area ("NO" in S35), a print-like image of that character is displayed; if the data is found not printable ("YES" in S35), a message indicating the unavailability of printing is displayed (S38), and the corresponding text appears on the display unit (S40).