iPhone Applications:
Apple applications are the only type of software you can use with the iPhone
operating system. (the iPhone has a strong computer system built-in but Apple
restricted it only to read registered app's so they control the functions and
products that are used by iPhone users)
The App Store:
To use the App store, you will need to open an account that includes your credit
card details. (Don't worry, the Account you open will matches only one device,
and you can use the username and password to download software etc.) , tap your
itunes Store icon from the device, and start browsing through the app store.
iPhone Applications and categories.
On the Apple store you will find on the Doc section the next options: featured,
categories,top 25, search and updates.You will find the most popular applications
for downloadingon top 25, which gives you 3 options; top paid, top free and top
grossing.
 

 
To enjoy free applications go to top free and download various free applications
(some of them are free trials of paid applications)To search for a category of an
application go to categories.
 
 
To search for a specific application go to search. You can download and store up
applications from itunes straight from your computer as well, and itunes will
synchronize your iPhone the next time you update it. Any software you download
will receive an icon and you'll have to dig through menus to find it. Applications
get free updates and will appear on the main menu screen on the apple store icon.
Next: 7.iPhone Ring tones

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