The central component of the iOS SDK is Xcode, Apple’s interactive development environment (IDE). Xcode facilitates building apps for OS X, iOS and WatchOS. Xcode includes the interface, the LLVM compiler, instruments and iOS simulator tools that make development and testing possible without an Apple device. Apple allows free download and use of Xcode, the only requirement being an Apple ID.
Developers can build and test apps without charge. To have apps considered for the app store, however, developers must subscribe for $99 individual or organization membership or $299 enterprise iOS developer program membership. All apps are subject to Apple approval. Apple restricts use of Java, .NET and Flash on iOS, generally limiting third-party code.
Discover more about Apple's Xcode IDE