Abstract: A general-purpose system for enabling the user to easily enter characters whose contents are hard to understand at a glance, such as bar codes, by using a general-purpose application program such as a wordprocessor is provided. For this purpose, a printer driver comprising a font file storing a display font and a bar code record font corresponding to the display font and a conversion function of converting display font codes into record font codes is provided. When a bar code is entered in an application program, a legible display font corresponding to the bar code can be used. On the other hand, when the bar code is printed, the printer driver compatible with a given printer converts the display font into a bar code record font and supplies the bar code record font. Thus, a high-accuracy bar code is printed in accordance with the standard.