= Live tiles that display updated information on colored rectangles on the start screen. Developers need to tap into this capability to show, for instance, current temperatures to go with weather apps or scores to go with sports apps.

= Embedding software services in applications. For example, interfacing applications with the system search feature enables searching with that app for a given term. The example he used was searching for references to Jessica Alba -- who participated in the Windows Phone 8 launch this week -- in Internet Explorer, Outlook emails, Xbox, Finance, etc.

= Enabling the Windows 8 snap feature in apps so users can display them in a quarter of the screen at either side, to keep them visible even while working in another app. It's a way to track, say, the stock market while doing other work in Excel.

"They're all springboards for your imagination," Ballmer says.

Presenters at the keynote spent time explaining how with the new WinRT application architecture enables easy reuse of code for Windows 8 and Windows Phone 8. The apps written for one can't run in the same form on the other, but due to a common set of APIs for the two operating systems, entire blocks of code can be written for one and inserted in the other. This makes it much simpler to write apps for both platforms.