Office 15 will be Included in ARM version of Windows 8

Microsoft has announced that they are developing the operating system Windows 8 for ARM architecture processor (32 bit RISC), which has been widely used in smartphones and tablet devices.
So later on, the tablet with Windows 8 will use the ARM version of Windows 8, not the x86 version is designed for desktop computers. 

The news surprised him was, in the ARM version of Windows 8, already available in the Office 15 version of the application built-in (default), with access to Word, Excel, PowerPoint, and OneNote. Office 15 is the office software that will continue in Office 2010.
Microsoft also confirmed, Office 15 is designed for ARM can be used for touch-screen navigation.
There has been no confirmation whether the presence of a built-in Office 15 on Windows 8 will make the price of its tablet devices become more expensive or Microsoft giving away free to the tablet vendor.
Because Windows 8 ARM is a version specifically designed for mobile devices, so this version can not run a Windows application that is built for Intel x86 architecture computers (desktop computers).
Microsoft had asserted, that the ARM version of Windows 8 will not be running, emulates, and porting applications to the desktop computer.
  As such, Microsoft will make Windows applications in a separate version of the ARM.