Trees

Trees

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Many different parts of the Windows XP interface are represented by hierarchical trees, like the one in Figure 3-33. This collapsible tree interface can be found in Explorer (representing drives and folders), the Registry Editor (representing Registry keys), and Device Manager (representing installed devices).

Figure 3-35. The Folder Tree is an efficient and useful way to visualize and navigate the hierarchy of your filesystem

In most cases, displaying all entries in all branches of a tree would take too much time, and would certainly be unwieldy. Instead, branches are " collapsed " and only the top levels are shown; you can expand any branch by clicking the plus sign (+), and then collapse any branch by clicking the corresponding minus sign (-). You can also double-click any branch to expand it, and again to collapse it. If no plus sign (+) appears, then the entry has no "children" and cannot be expanded further.

Navigating trees with the keyboard is often more convenient than using the mouse. As with listboxes (discussed earlier in this chapter), you can jump to any branch by typing the first letter (or first few letters ) of its name . This works regardless of the depth of the entry, but only on entries that are currently visible. Use the right arrow key to expand the currently selected branch, or the left arrow key to collapse it; if the branch is already collapsed, the left arrow key jumps to the parent. The Backspace key also jumps to the parent, but it never collapses branches. Finally, the asterisk key (*) expands all branches from the current location.