A major update to Windows Phone introduced in late 2012. It replaced the Windows CE operating system with a version of the Windows 8 operating system. Phones such as the Lumia 900, which cannot be upgraded to Windows Phone 8 may obtain some of its features with a Windows Phone 7.8 update.
Windows Phone/Tablet Compatibility
Windows Phone 8 apps do not run in Windows RT, 8 or 10 tablets. Microsoft took the opposite direction of Apple. Windows desktop apps run on Windows tablets, but Windows Phone apps do not. In contrast, iPhone apps run on iPads, but Mac desktop apps do not run on iPhones or iPads. See Windows Phone
and mobile compatibility
Windows Phone 8 Start Screen
The most visible difference between WinPhone 7 and 8 is the expanded start screen. WinPhone 8 uses all the screen real estate and lets the user adjust the tile size. (Image courtesy of Microsoft Corporation).
Although a lot of programming code across Windows devices is shared by developers, the executable apps that run on Windows phones do not run on Windows 8 or RT tablets.