Mountain Lion, Apple's new operating system for Mac users, sold 3 million copies in just the first four days of its availability.
Apple says the figure makes it the fastest launch of an operating system of the company ever. Mountain Lion OS X was released on July 25.
Mountain Lion brings features from the iPhone and iPad to the Mac. The enhancements include tight integration with Apple's online storage service, iCloud, and a "Notification Center" that shows incoming mail, calendar reminders and other events.
Apple charges $20 for the software. That pays for downloads for all of a buyer's personal computers. The technology giant also provides the OS for free, to buyers who bought a Mac on or after June 11.
With inputs from Associated Press