Why can't I play my game while an update is downloading?

[WorldsApart]

This is annoying as hell and it's one of the reasons I hate modern gaming. That's great, you're probably giving me some useless crap I don't need or want. Or better yet this update is probably going to require new drivers for everything. In the meantime I can't play the game I was perfectly fine playing yesterday. Thanks ALWAYS ON...

[Zefar]

You can't play a game while it's updating because files are being overwritten or changed and the game itself would crash constantly during this process as files are not in the way they are supposed to be.

Updates to games doesn't need new drivers but it's probably a good idea to update your graphics drivers once in a while with a clean re install of them. Because there have been times when graphic drivers have made games run a lot better.

[aiusepsi]

Originally posted by Zefar:

You can't play a game while it's updating because files are being overwritten or changed and the game itself would crash constantly during this process as files are not in the way they are supposed to be.

Steam doesn't update the files in place. It creates a new version of each updated file in the steamapps/downloading folder, by reading un-updated bits from the old files and downloading new bits. Then once it's finished constructing the new versions of all the updated files, it swaps in the new for the old.

That final swap can't be down while the game's running, but all the downloading can, as the original install is only read from and so stays pristine. There's no technical reason for Steam having to stop you playing while an update is happening to that same game.