The Windows 8 On-Screen Keyboard makes it possible to use computer without a physical keyboard and can be set as default input device.
Here is how to set up this virtual keyboard so that it can be used directly every time after logging into Windows 8 :
Open Control Panel (either search for Control Panel from charms bar by moving the mouse pointer to extreme right side of screen and selecting “Search” .
Or right click on the bottom left side of Windows 8 screen which actually had Start button prior to Windows 8 :).
Select “Ease of Access” and from within that, choose “Use the computer without a mouse or keyboard”.
Next, enable the option “Use On-Screen Keyboard”.
From now on, every time you login to Windows 8, the virtual keyboard will be the default input for typing and can be used through mouse clicks.