No, iOS is not written in C. iOS is written in a variety of languages, including Swift, Objective-C, and C++. When developing an iOS app, developers typically use the Xcode development environment, which allows them to write apps in a variety of languages and frameworks. Additionally, developers can use third-party libraries and frameworks to extend the capabilities of their apps. If you're new to iOS development, I recommend starting with Swift, as it is the language used most frequently for developing apps for iOS.