A well known difference between Mac and PC computers is the size of their disks. This is due to the way of saving files on disks. Any file displayed on the screen can be considered as a database D1 of objects to be displayed and a graphic database D2 of orders to be executed to display these objects on the screen. On Mac machines, only D1 is saved on disk. On PC, both D1 and D2 are saved on disk. As D2 is a much bigger file than D1, PC's always needed more disks.