Fullscreen "pop" or resolution change/fit?

On many commerical games, even when you run them at the same exact resolution you use for your monitor natively, the game kinda does a "resolution change" like the old-day style of full screen, the monitor goes black for a second and when you alt+tab or alt+f4 or alt+enter away from the game, it "pops" back, even though the game is running in the same resolution as the desktop is. I wondered exactly why it does this and if it's possible to have C2 games "lock" to the resolution you run them in like that?

I'm not sure what the question is exactly..

What would this locking consist of?

It's hard to explain this, but if you try, let's take for example, a 3D game of some sorts released through Steam by a major developer, more often than not when you double-click to start the game, your monitor will do a little "switch" to black and come back again, ALL old games from the 90's that ran full-screen would do this, but in recent times I only really see it on the 3D games and the line, I mean, I can say right now that Duke Nukem Forever does it on my 1280x1024 4:3 screen, I'm just not sure what to call it when the screen does the "switch" to black briefly, and when you run a Scirra (or even MMF) game it never does this, it just goes fullscreen like a Youtube video does (obviously, it's HTML5).

And you want the screen to go black?

Should be relatively easy right?

No, it's not the effect of it, I just want to figure out what causes the game to "adapt" to the resolution rather thansit on top, you notice how with alot of games if you you alt+tab out of it, the screen goes off for a second and then the desktop shows, but then if you click on the game it just shows regularly when the game is windowed? Then you might alt+enter to make it fullscreen and it goes black and then appears in true fullscreen? I guess I want to know what the true fullscreen mode is, vs the sort of fullscreen-windowed-windowless mode that C2 uses.