WP8 will have a 'common core' with Windows 8 on the desktop, which should make it easier for developers to carry over apps from one platform to the other. The new mobile OS supports 1280x768- and 1280x720-resolution displays.
However, owing to hardware limitations, or what Microsoft calls "a generation shift in technology", Windows Phone 7 devices won't be able to run the full WP8 OS. Instead they will get Windows Phone 7.8, a version that includes some, but not all, of WP8's enhancements.
WP8 brings with it tweaks to the Metro user interface (above), with live tiles now available in three sizes.
Microsoft brought out the Skype for Windows Phone beta in February, but Windows Phone 8 goes a step further with full Skype integration. The image above shows a handset receiving a video call on Skype.
The shot above shows a WP8 handset receiving a phone call via Skype.
There will be more colours and themes in Windows Phone 8's UI.
Enterprise users will have the option of creating a company hub where they can keep apps, profile info and alerts in one place.
Above, a Nokia Lumia 900 runs Windows Phone 7.8, an upgrade of the OS for existing Windows Phone 7.5 devices.
The Lumia 900 on the left is running Windows Phone 8, while the Lumia 900 on the right is loaded with Windows Phone 7.8. The differences here are fairly subtle: Windows Phone 7.8 includes the new start screen with different-sized tiles, although it takes up the whole screen.
Microsoft has said that Windows Phone 8-based smartphones will arrive in the autumn, from Huawei, Nokia, Samsung and HTC. Read Windows Phone details revealed: No upgrade for Mango Phones for more on WP8.