If a window isn't long enough to display its contents completely, Windows adds a vertical scroll bar to the right side of the window. If the window isn't wide enough, Windows adds a horizontal scroll bar. If it's neither long enough nor wide enough, Windows adds both kinds of scroll bars. Figure C-7 shows a window with vertical and horizontal scroll bars.
Scroll bars offer an easy way to navigate through a window with the mouse. They also provide useful information about the contents of the window.
In Figure C-7, notice the rectangular scroll box in each scroll bar. The position of this box within the scroll bar tells you where you are in the window itself. In the vertical scroll bar, for example, the scroll box is situated about 10 percent of the way down the bar. That means that roughly 10 percent of the window's contents lie above your current position in the window.
Figure C-7. Scroll bars provide information about the contents of a window and allow you to move quickly from one part of the window to another.
Now notice the size of the scroll boxes relative to the length of the scroll bars. The vertical box is about 5 percent of the length of the scroll bar itself. That means that about one twentieth of the window's vertical extent is currently visible within the window frame. The horizontal scroll bar works the same way.
For navigation purposes, you can use scroll bars in the following ways: