The original iPhone first shipped with an operating system called iPhone OS.
Apple introduced the iPhone OS with the first iPhone in 2007. The software combined a touch-based interface with core technologies derived from Mac OS X, including a Unix-based foundation and advanced graphics capabilities. At launch, Apple did not provide a third-party software development kit or an App Store.
Apple renamed the platform iOS in 2010, around the release of iOS 4. The new name reflected the system’s expansion beyond the iPhone to products such as the iPod touch and iPad.
This creates a frequent historical mix-up: “iOS” is the modern name, but “iPhone OS” was the original branding. The first iPhone also lacked features later considered standard, including copy and paste, multitasking for third-party apps, and an App Store.