Abstract: A data conversion apparatus is able to convert data created by every information processing software program into data of a predetermined common format style without modifying each information processing software program. When an operator enters a data output command, original data created by the information processing software program is transferred through an operating system (OS) to a printer driver. The printer driver converts the original data into bit map data, and then a conversion driver added to the printer driver converts the bit map data into TIFF data. The TIFF data is memorized in a memory together with corresponding original data. If TIFF data is displayed on a screen of a personal computer by using viewer software, data created by every information processing software program can be viewed with ease.