While you move your cursor, you will see a box with the yellow lines for the section you will capture. However, it is hard to have the whole screen: the window and the taskbar at the bottom.
It is actually very easy if you know the tricks, the same as to capture a small portion of the screen. Just click one corner and drag to the diagonal corner, then release the mouse cursor. The full screenshot is now ready.
Please visit Snagit official website www.techsmith.com for details.