DirectDraw supports both Mode 13 and Mode X display modes. Mode 13 is the linear unflippable 320x200 8 bits per pixel palettized mode known widely by its hexadecimal BIOS mode number: 13. For more information, see Mode 13 Support. Mode X is a hybrid display mode derived from the standard VGA Mode 13. This mode allows the use of up to 256 kilobytes (KB) of display memory (rather than the 64 KB allowed by Mode 13) by using the VGA display adapter's EGA multiple video plane system.
On Windows 95, DirectDraw provides two Mode X modes (320×200×8 and 320×240×8) for all display cards. Some cards also support linear low-resolution modes. In linear low-resolution modes, the primary surface can be locked and directly accessed. This is not possible in Mode X modes.
Mode X modes are available only if an application uses the DDSCL_ALLOWMODEX, DDSCL_FULLSCREEN, and DDSCL_EXCLUSIVE flags when calling the IDirectDraw2::SetCooperativeLevel method. If DDSCL_ALLOWMODEX is not specified, the IDirectDraw2::EnumDisplayModes method will not enumerate Mode X modes, and the IDirectDraw2::SetDisplayMode method will fail if a Mode X mode is requested.
Windows 95 and Windows NT do not support Mode X modes; therefore, when your application is in a Mode X mode, you cannot use the IDirectDrawSurface3::Lock or IDirectDrawSurface3::Blt methods to lock or blit to the primary surface. You also cannot use either the IDirectDrawSurface3::GetDC method on the primary surface, or GDI with a screen DC. Mode X modes are indicated by the DDSCAPS_MODEX flag in the DDSCAPS structure, which is part of the DDSURFACEDESC structure returned by the IDirectDrawSurface3::GetCaps and IDirectDraw2::EnumDisplayModes methods.
Mode X modes and some linear low-resolution modes are not supported on Windows NT.