How do software updates for purchased apps work? That’s among the many questions users have about the Mac App Store. With the Mac App Store just over a day old, updates for purchased apps are already appearing in the Store.
In our Mac App Store FAQ, our thoughts on how updates work were based on hunches, since at the time, app updates were not available. Now they are, and in case you’re wondering how minor software updates through the Mac App Store work, here’s a look. (There’s still a question as to how major upgrades, such as version 1.0 to version 2.0, will work with the Mac App Store.)
Updating Angry Birds for Mac
When I opened the Mac App Store today, the Updates button at the top of the Mac App Store window had a numerical indicator on it, showing that I had one update available for Angry Birds.
I clicked on the button, and the update was listed for me. It showed the app that needed updating, the version number of the update, the date of the update’s release, and a description of the update. In this particular example, with the Angry Birds version 1.0.1 update, “Some error messages made more readable.” 
When I clicked on the Update button, I had to sign into my account with my user name and password. Then the download starts, and a progress bar appears. You can pause the download, which I did to see if I could find the location where the app was being downloaded. It wasn’t downloading to the Downloads folder; it was downloading to a folder identified with a nine-digit number in ~/Library/Application Support/AppStore.
When I resumed the download, I noticed that the Angry Birds app icon does not show a progress bar, as iOS app icons do when they are being updated. The 41.1MB download took about three minutes for me. 
The status in the Mac App Store Updates section changed to Installing after the download completed. I noticed that the Angry Bird icon in my Applications folder “blinked” and I verified that it was version 1.0.1 by checking Get Info. The status changed to Installed, and the folder with the nine-digit name in the ~/Library/Application Support/AppStore folder disappeared—and there was no sign of it in the Trash.
And that was it. Version 1.0.1 of Angry Birds ran smoothly. If I hadn’t paused the update and poked around my Mac to find files, the complete, barely-noticable process would’ve taken less than five minutes. It’ll be interesting to see how bigger updates and major version upgrades has handled through the Mac App Store.
[Roman Loyola is a Macworld senior editor.]