Putting to sleep while updating

Nazli wrote:
Right now I'm downloading Mac OS X 10.5.6 update and my question is does putting the computer to sleep affects download? Because previously the computer was asleep for a while and then the package didn't work.

Never put a computer to sleep during an update. You can lose everything.
If you put it to sleep during a download, the download will terminate improperly and may need manual removal from the HD.
You can let the screen sleep, but never the computer, during any operation.