The next major upgrade of Microsoft's operating system, Windows 8 for PCs, tablets and laptops, will be released to manufacturers in August and will ship commercially in October.

Microsoft had not previously given a firm shipping date, but said that the OS would be commercially available before the end of the year.

Microsoft will coincide the release of Windows 8 with the activation of the Windows Store and start charging for applications. During the test period, these have been free.

The company announced the release at its Worldwide Partner Conference in Toronto.

There, Microsoft CEO Steve Ballmer said that this is "an epic year" for Microsoft new product upgrades. He called Windows 8 "the biggest deal for our company in at least 17 years."

The timetable Microsoft announced today applies not only to the Windows 8 version for x86 chips from AMD and Intel, but also for Windows RT, the Windows 8 version that will run on ARM-based devices. It will not be sold as a stand-alone OS.

Windows RT will ship embedded with its devices, which will be made by Microsoft and third-party hardware partners.

The OS will also be available for upgrades for people with PCs running Windows 7, Windows Vista and Windows XP. Microsoft has already provided details about upgrade options and prices.

Microsoft has sold more than 630 million licenses of Windows 7, and more than half of enterprise desktops today are running it.