From the time of the iPhone's inception, there have been 4 generations accompanied by four major updates of Apple's 'On the go' OS, named iOS. Every new version of iPhone and its iOS add to another aspect to the mobile device: the iPhone 3g supplement 3g network enhancements and global positioning; the iPhone 3GS was enhanced with a compass, better processor and higher resolution camera, which included video; the iPhone 4 has two cameras for FaceTime video calling and a higher-resolution display. Because of these differences between each improvement of iPhone, new iPhone applications have been developed with different iPhone generation. So as to make up for all of these changes and up compatibility between the different iphone types, programmers compile many versions of their applications for each iOS. Ex, not every app may take advantage of iOS 4's multitasking performance. And some applications require a specific iOS type to be present in order to work perfectly.

The majority of apps with varying iPhone versions not only cater to bugfixes, but also enhance increased functionality, allowing every last new functions the new iOS includes. Occasional a user will have to use a previous application type, as the new type may no longer have support for their specific device. To clear any confusion, manufacturers can point out the minimum iOS type needed to use their particular app. 3 applications that have specific version changes to maintain compatibility are Atomic Web Browser, Meebo, and instapaper. Next let us have a look at how the apps have evolved to work with each new iPhone version.

The 1st app which has new types for alternate iPhones is Atomic Web Browser. This app has changed many time so as to maintain functionality across all types of iPhone. The latest type, 4.0.1 (as of writing, includes a TV out function for both iPhone4 and iPad.) Also, the latest Atomic Web Browser version contains numerous fixes for bugs that were a result of iOS 4.2 Similar to Atomic Web Browser, Meebo is interoperable with the iPhone, iPod touch and iPad; but, the app requires that the device is using iOS 3.1.3 or later. fixes that will reinforce future iOS functionality. One of the recent generation of Meebo, 1.3.1, now has multitasking support as domany other apps that have been updated to take advantage of iOS 4's new features. fix from version 2.3.1 that caused a crash on iPads running iOS 3.2 In addition, Instapaper previously required iOS 3.0 to be installed, but at present, this app needs a minimum iPhone OS 3.1.

These apps are just a few examples of how programmers are constantly creating different upgrades for every new iOS update that is released for the iPhone, iPad Touch, and iPad. With each update created for the iPhone OS there are new operability and functionality, but the differences also spawn bugs and compatibility concerns with previous versions. Regardless of what version iPhone you have, it is safe to say that there is an app version that is specifically for the phone.