Windows 8 update or Windows 8.1 (codenamed Windows Blue) will be distributed through the Windows Store. During the Wired Business Conference in New York, Julie Larson-Green, Vice President of the Windows division has also confirmed that a Developer Preview of Windows Blue will be released at Microsoft Build Developer Conference to be held in San Francisco from June 26 to 28th. However, the Microsoft executive escaped to comment on the final availability of the Windows 8.1, but the RTM (release to manufacturing) build is expected to arrive at the end of the August.
Microsoft has not yet outlined its plan related to Windows 8 update, but it seems pretty clear that Windows 8.1 represents a substitute for Service Pack, the full-bodied package released for previous operating system distributed via Windows Update so far. Presumably, Windows Blue might be called a Feature Pack as it includes many new features as well as several optimizations that improve the overall user experience that are missing in the current version of the operating system.
One of these is the Start button. Julie Larson-Green also said that the traditional button might be useful for some people and users would like to display it on the screen all the time. However, the button will only serve to access the Start Screen with live tiles despite the old Start menu.
A public preview of Windows 8.1 will be released at the Build conference in late June, and the final version will be available on the Windows Store, usually used for downloading and updating Modern apps.