iPhone Apps and File Extensions

Languages

Apps for the iPhone are primarily developed in Objective-C. This is an object-oriented programming language that is built atop the older C programming language. The syntax of Objective-C is similar to C and C++, and developers can integrate code from these languages directly into Objective-C programs. Source code files usually use the extension '.m' or '.mm' and header files with library data usually use the '.h' extension.

iPhone SDK

Apple provides iPhone app developers with a software development kit (SDK) to make app development quicker. The SDK contains library components that allow apps to access and use the features of both the iPhone's hardware and its iOS operating system with a minimum of code. These are in addition to other Objective-C based programming tools that Apple provides anyone for creating application interfaces and packaging different app components into a single program.

.Ipa File Extension

Apple has its own system for transferring packaged apps onto the iPhone for execution. To use these systems, programmers use the iPhone SDK to package program components into a '.ipa' files. iPhone developers then either use the SDK's tools for directly installing an .ipa package on iPhones and iPods, or go through Apple's procedures for uploading the package to Apple's App Store. Once an .ipa package is in the App Store, anyone can download the program onto their devices.

.Deb File Extension

While Apple's official channels for installing apps require the program components to be packaged in the .ipa format, there are third-party tools that let iPhone users transfer apps to their devices outside of the SDK's tools or the App Store. These alternative app repositories are legal, but Apple discourages its customers from circumventing its software controls, also known as 'jailbreaking,' in order to use them. Alternative repositories usually have programmers package their apps in the '.deb' format for user download.