There are two types of DDBs: discardable and nondiscardable. A discardable DDB is a bitmap that is discarded if the bitmap is not selected into a device context and if system memory is low. Device-dependent bitmaps are supported only for compatibility with applications written for earlier Windows versions. A developer writing a new application, or porting an application written for a previous version of Windows to the Win32 platform, should use device-independent bitmaps.