Photoshop users are often professionals working with images in truecolor. Images can be very large, and Photoshop users are expected to have adequate memory to load and manipulate large files. Adobe has chosen to optimize the speed of reading and writing in the Photoshop system, and this is reflected in the RLE compression incorporated in the PSD format. Files, therefore, are not as small as they might be using another compression method. Although this makes sense in the context of a Photoshop-equipped workstation, the lack of a superior compression scheme has probably prevented PSD from becoming more popular as a general-purpose interchange format. Because PSD is an application-specific format, expect it to change in the future. Under Microsoft Windows, Photoshop files are stored with the PSD suffix and can be identified by looking for the file ID value 8BPS. On the Macintosh, Photoshop files are resource-fork only, and data is recognized by the file ID value 8BPS. Earlier versions of the format had no compression and were tied to the Macintosh platform.