App store innards - handy knowledge for basic maintenance

Excellent review, includes a few that are new to me. Read the entire article for the full story, I'll be checking for leftover app versions in my iTunes app folder.

iPhone Atlas - Ted Landau - Five “under-the-hood” things you should know about App Store apps

1. Where are iPhone apps actually stored on a Mac ...

2. I opened the Mobile Applications folder. All the files there end in .ipa. What’s with that?

Consider ipa an abbreviation for “iPhone application.” ... use the shareware program Pacifist. Specifically:

1. Make a copy of the app that you want to check (say Koi Pond.ipa).
2. Change the name of the copied file to Koi Pond.ipa.pkg.
3. Click “Use .pkg” when the dialog appears asking what you want to do.
4. Open Koi Pond.ipa.pkg in Pacifist.

...
1. Via Pacifist, navigate to Payload > KoiPond.app >Info.plist. Extract this file.
2. Open the file using Property List Editor (or any other utility you have for opening .plist files).

From here, you can confirm the version number (CFBundleVersion) of the app. This should be the same number you’ll find in the Version item of the Summary tab, if you select Get Info for an app in iTunes.

Also in the .plist file, note the line that reads UIStatusBarHidden Boolean Yes...

3. There are several copies of some apps in the Mobile Applications folder (with names like Koi Pond.ipa, Koi Pond 1.ipa, Koi Pond 2.ipa etc.) What gives with that?

First the good news: If you’ve updated to iTunes 8, this should no longer happen.

Prior to iTunes 8, these duplicates accumulated each time you updated to a newer version of an app (or even redownloaded the same version). All downloads were retained, even though only the latest copy was used.

... If you still have duplicates hanging around, drag them to the Trash and delete them. You only need to retain the copy with the most recent modification date. If there is any doubt as to which copy to keep, go to Applications in iTunes and select Show in Finder from any app’s contextual menu. This will take you to the Mobile Applications folder with the active copy highlighted. That’s the one you want to keep.

Although they are usually harmless, these duplicates can occasionally cause problems...

4. Can I run apps on my iPhone that other people have purchased?

No and Yes. The system for apps works the same way as for music and video purchased from the iTunes Store. By default, App Store apps can only be run on iPhones and iPod touches synced to the computer used to purchase the software. However, a user can authorize up to 5 computers to have access to their iTunes Store purchases. Thus, to use an app purchased by a friend...