SDL_SetVideoMode man page
SDL_SetVideoMode — Set up a video mode with the specified width, height and bits-per-pixel.
SDL_Surface *SDL_SetVideoMode(int width, int height, int bpp, Uint32 flags);
Set up a video mode with the specified width, height and bits-per-pixel.
If bpp is 0, it is treated as the current display bits per pixel.
The flags parameter is the same as the flags field of the SDL_Surface structure. OR'd combinations of the following values are valid.
Create the video surface in system memory
Create the video surface in video memory
Enables the use of asynchronous updates of the display surface. This will usually slow down blitting on single CPU machines, but may provide a speed increase on SMP systems.
Normally, if a video surface of the requested bits-per-pixel (bpp) is not available, SDL will emulate one with a shadow surface. Passing SDL_ANYFORMAT prevents this and causes SDL to use the video surface, regardless of its pixel depth.
Give SDL exclusive palette access. Without this flag you may not always get the the colors you request with SDL_SetColors or SDL_SetPalette.
Enable hardware double buffering; only valid with SDL_HWSURFACE. Calling SDL_Flip will flip the buffers and update the screen. All drawing will take place on the surface that is not displayed at the moment. If double buffering could not be enabled then SDL_Flip will just perform a SDL_UpdateRect on the entire screen.
SDL will attempt to use a fullscreen mode. If a hardware resolution change is not possible (for whatever reason), the next higher resolution will be used and the display window centered on a black background.
Create an OpenGL rendering context. You should have previously set OpenGL video attributes with SDL_GL_SetAttribute.
Create an OpenGL rendering context, like above, but allow normal blitting operations. The screen (2D) surface may have an alpha channel, and SDL_UpdateRects must be used for updating changes to the screen surface.
Create a resizable window. When the window is resized by the user a SDL_VIDEORESIZE event is generated and SDL_SetVideoMode can be called again with the new size.
If possible, SDL_NOFRAME causes SDL to create a window with no title bar or frame decoration. Fullscreen modes automatically have this flag set.
Whatever flags SDL_SetVideoMode could satisfy are set in the flags member of the returned surface.
The bpp parameter is the number of bits per pixel, so a bpp of 24 uses the packed representation of 3 bytes/pixel. For the more common 4 bytes/pixel mode, use a bpp of 32. Somewhat oddly, both 15 and 16 will request a 2 bytes/pixel mode, but different pixel formats.
The framebuffer surface, or NULL if it fails. The surface returned is freed by SDL_Quit() and should nt be freed by the caller.
SDL_LockSurface, SDL_SetColors, SDL_Flip, SDL_Surface