Microsoft announced Windows 10, the next version of its Windows operating system. Microsoft will launch a Windows Insider Program for users who want to run very early beta software. This first preview will be available for laptops and desktops.
New operating system will have a different user interface between different screen sizes. A few features of Windows 7 is going to be brought back, redesigned start menu with the re-sizable tiles of Windows 8 start screen. Windows 8 Metro apps can now also be opened in a windowed mode on the desktop, so you aren’t taking into the full-screen mode by default.
There will be one store, one way for applications to be discovered, purchased and updated across all of the devices. Whether a game or a line of business application is being developed, there will be one way to write a universal app that targets all the devices.
Windows 10 will allow to work with multiple desktops. You can grab the apps from multiple desktops and move them around. Command line has been improved. New operating system in touch enabled machines will have a Windows 8 Start Screen,
Source: Windows Blog