Windowed vs. full-screen mode
Direct3D applications can run in either of two modes: windowed or full-screen. In windowed mode, the application shares the available desktop screen space with all running applications. In full-screen mode, the window that the application runs in covers the entire desktop, hiding all running applications (including your development environment). Games typically default to full-screen mode to fully immerse the user in the game by hiding all running applications.
Code differences between full-screen mode and windowed mode are very small.
Because an application running in full-screen mode takes over the screen, debugging the application requires either a separate monitor or the use of a remote debugger. One advantage of a windowed-mode application is that you can step through the code in a debugger without multiple monitors or a remote debugger.
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