Microsoft on Monday for the first time revealed a shipping schedule for its forthcoming Windows 8 operating system.

The OS will be released to manufacturing in the first week of August, and new systems running the software will be generally available to the public by the end of October. The news was announced by Tami Reller, CFO for Microsoft's Windows group, at the company's Worldwide Partner Conference in Toronto.

Enterprises will be able to start downloading final Windows 8 bits "as early as August," said Reller, who added that more than 50% of enterprises have already upgraded to Windows 7. Windows 8 will be available in 105 languages in more than 200 markets.

The new operating system will be available in just four editions: Windows 8, Windows 8 Pro, Windows 8 Enterprise, and Windows 8 RT. The last is Microsoft's official name for Windows On ARM, which will run on tablet chips manufactured by Qualcomm, Motorola, and Nvidia. By comparison, Windows 7 was available in six editions, including Starter, Home Basic, Home Premium, Professional, Ultimate, and Enterprise.

Users of Windows XP, Windows 7, or Windows Vista will be able to purchase and download Windows 8 Pro for just $39.99. The upgrade program, which starts with Windows 8's general availability in October and runs through January 31, 2013, also lets users install Windows Media Center for free once they've completed the upgrade.