I'm not sure if you want to know about storage on the iPhone itself, or storage by iTunes in the backups, so I'll take a stab at both. :)
See here for a more in-depth analysis, but the basic gist is that the .mddata
files are typically SQLite databases (occasionally encrypted), while the corresponding .mdinfo
files are the metadata associated with them. (Older versions of iTunes used .mdbackup
files.)
Here's a more practical description of retrieving data from an existing iPhone/iPod backup, and another one which does so with the more recent format. Also, there's this presentation that dives into the format a bit. Here's a blog entry about deciphering the obfuscated filenames, and finally, here's a StackOverflow discussion about decrypting the encrypted .mddata
files (which didn't end in a resolution of any kind).
On the iPhone itself, many applications store their data in a SQLite database directly because of the simplicity of doing so. Also, the Core Data ORM uses it under the hood, although that's really just an implementation detail.
But, as you've noted, there's no requirement to use SQLite; applications can store data in something as simple as a plain text file or XML document, or as complicated as a database of their own making.
For what it's worth, have you taken a look at the Apple iPad Keyboard Dock Wired Keyboard?
It doesn't have a number pad but otherwise is a full sized keyboard that shouldn't even need bluetooth.
Of course I am assuming that it will work with an iPhone even though it was made for an iPad.
Best Answer
Your guess was correct.
.ipa
stands for iOS App Store PackageEach
.ipa
file is compressed with a binary for the ARM architecture that can only be installed on iOS devices. If you change the extension to.zip
you will be able to unzip it and view the contents.