SAN JOSE, Calif. — In the history of Apple software, few services have been as important and influential as iTunes. It upended the music industry and popularized a new way to buy music, allowing people to purchase songs for a dollar.

On Monday, at its annual Worldwide Developers Conference, Apple said it was killing iTunes on Mac computers — a long-anticipated development that has already occurred on iPhones. The end of iTunes was the most prominent announcement in an opening keynote address that also highlighted a separate app store for the Apple Watch, a $6,000 Mac and the company’s continued emphasis on privacy.

For years, Apple users have complained that iTunes was outdated, particularly as streaming music over the internet gained popularity. Apple resisted change for years because iTunes was such a fundamental feature of its Mac computers. But with its new version of Mac software, Apple took the leap and split iTunes’ services into three separate apps.