iOS, originally known as iPhone OS, is Apple's proprietary mobile operating system, first unveiled in January 2007 alongside the initial iPhone and released in June of the same year. Developed under Steve Jobs' guidance through an internal competition, Scott Forstall's team created the OS by adapting macOS, making it a Unix-like system. Initially, the system only supported web applications, but Apple quickly introduced a native Software Development Kit (SDK) and launched the App Store in July 2008, which rapidly expanded to host millions of apps. Today, iOS is the world's second most widely installed mobile operating system, serving as the foundation for other Apple platforms like iPadOS, tvOS, and watchOS. Major versions are released annually, and its App Store had grown to offer over 3.8 million applications by December 2023, solidifying its status as a dominant mobile ecosystem.