C H A P T E R 9

User Input

The Keyboard

The keyboard’s primary use is to enter text. The keyboard may also be used for navigation, but it should always be an alternative to using the mouse. For more information about using the keyboard instead of the mouse, see “Keyboard Focus and Navigation” (page 182).

Important

Avoid assigning any key combinations listed in the tables in this section to commands other than those specified in the tables. Even if your application doesn’t support all the keyboard equivalents shown, don’t assign unused combinations to commands that conflict with those specified in this section.

The Functions of Specific Keys

There are four kinds of keys: character keys, modifier keys, arrow keys, and function keys. A character key sends a character to the computer. When the user holds down a modifier key, it alters the meaning of the character key being pressed or the meaning of a mouse action.

Note: Not all the keys described here exist on all Macintosh keyboards. Don’t depend on a key as the only way for users to accomplish a task.

Character Keys

Character keys include letters, numbers, punctuation, the Space bar, and nonprinting characters—Tab, Enter, Return, Delete (or Backspace), Clear, and Escape (Esc). It is essential that your application use these keys consistently.

166The Keyboard

Apple Computer, Inc. June 2002

C H A P T E R 9

User Input

Space Bar

In text, pressing the Space bar enters a space between characters.

When full keyboard access is turned on, pressing the Space bar selects the item that currently has the keyboard navigation focus (the equivalent of clicking the mouse button).

Tab

In text-oriented applications, the Tab key moves the insertion point to the next tab stop. In other contexts, Tab is a signal to proceed; it means “move to the next item in a sequence.” The next item can be a table cell or a dialog text field. Shift-Tab navigates in the reverse direction. Pressing Tab can cause data to be entered before focus moves to the next item. For more details about navigating with the Tab key, see “Keyboard Focus and Navigation” (page 182).

Enter

Most applications add information to a document as soon as the user enters it. In some cases, however, the application may need to wait until a whole collection of information is available before processing it. The Enter key tells the application that the user is through entering information in a particular area of the document, such as a text field. While the user is entering text into a text document, pressing Enter has no effect.

If a dialog has a default button, pressing Enter (or Return) is the same as clicking it.

Return

In text, the Return key inserts a carriage return (a line break) and moves the insertion point to the beginning of the next line. In arrays, the Return key signals movement to the leftmost field one step lower (like a carriage return on a typewriter). Like Tab, pressing Return can cause data to be entered before focus moves to the next item.

If a dialog has a default button, pressing Return (or Enter) is the same as clicking it.

Apple Computer, Inc. June 2002

C H A P T E R 9

User Input

Delete (or Backspace)

Generally, if an item is selected, pressing Delete (or Backspace) removes the selection without putting it on the Clipboard. If nothing is selected, pressing Delete removes the character preceding the insertion point, without putting it on the Clipboard. The Delete key has the same effect as the Delete command in the Edit menu.

Note: The Delete key is different from the Forward Delete key (labeled Del), which removes characters following the insertion point. See “Forward Delete (Del)” (page 175).

The Option key can be used to extend a deletion to the next semantic unit (such as a word). The Command key can extend a deletion to the next semantic unit beyond that supported by Option. Recommended key combinations for text applications are Command-Delete to delete the previous word and Command–Forward Delete to delete the next word. Option-Delete could delete either the word containing the insertion point or the part of the word to the left of the insertion point, depending on what makes the most sense in your application; Option–Forward Delete could delete the part of the word right of the insertion point.

Clear

The Clear key has the same effect as the Delete command in the Edit menu: It removes the selection without putting it on the Clipboard. Not all keyboards have a Clear key, so don’t require its use in your application.

Escape

The Escape (Esc) key basically means “let me out of here.” It has specific meanings in certain contexts. The user can press Escape in the following situations:

■in a dialog, instead of clicking Cancel

■to stop an operation in progress (such as printing), instead of pressing Command-period

■to cancel renaming a file or an item in a list

■to cancel a drag in progress

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Apple Computer, Inc. June 2002

C H A P T E R 9

User Input

Pressing Escape should never cause the user to back out of an operation that would require extensive time or work to reenter. When the user presses Escape during a lengthy operation, display a confirmation dialog to be sure that the key wasn’t pressed accidentally.

Modifier Keys

Modifier keys alter the way other keystrokes or mouse clicks are interpreted. You should use these keys—Shift, Caps Lock, Option, Command, and Control— consistently as described here.

Shift

When pressed at the same time as a character key, the Shift key produces the uppercase alphabetic letter or the upper symbol on the key.

The Shift key is also used with the mouse for extending a selection or for constraining movements in graphics applications. For example, in some applications pressing Shift while using a rectangle tool draws squares.

Caps Lock

When activated, the Caps Lock key has the same effect on alphabetic keys as the Shift key, but it has no effect on nonalphabetic keys. When the Caps Lock key is down, the user must press Shift to type the upper character on a nonalphabetic key.

Option

When used with other keys, the Option key produces special symbols. The Key Caps application shows which keys generate each symbol.

The Option key can also be used with the mouse to modify the effect of a click or drag. For example, in some applications pressing Option while dragging an object makes a copy of the object.

Apple Computer, Inc. June 2002