This chapter describes input devices. The user interacts with the operating system through input devices such as a keyboard, a mouse, a track ball, a pen, a graphics tablet, and a joystick. This chapter focuses on standard keyboard and pointing devices, with special emphasis on the mouse.
Users employ input devices to:
Manipulate elements (moving a slider, or moving or copying elements)
Select elements (identifying or grouping elements for subsequent interaction)
Activate elements (choosing elements such as an action choice that initiates a subsequent action)
Most users are familiar with using keyboards to interact with computers. The keyboard should allow the user to perform all of the functions available on the interface. Users also employ keys to augment pointing-device functions.
Keyboards differ in the number and type of keys available. This guide uses a model to describe keyboards and keys. The model does not correspond directly to any existing keyboard, but it assumes a keyboard with a standard set of keys. Appendix B, “Keyboard Model and Key Bindings” lists the keys that comprise the model, along with their corresponding functions.
In addition to the standard letter, number, and character keys, the keyboard model has the following special keys:
Printing character keys: /, \ , and !
Modifier keys: Ctrl, Alt, and Shift
Function keys: F1 through F10
Arrow keys, also called directional keys: Left Arrow, Right Arrow, Up Arrow, and Down Arrow
The following additional keys:
Backspace
Backtab
Begin
Cancel
Delete
End
Esc
Help
Insert
Menu
PageDown
PageUp
Enter
Return
Spacebar
Tab
The following optional keys (which, although useful, are either unnecessary or can be created by combinations of other keys):
CapsLock
Copy
Cut
keypadEnter
Home
ModeSwitch
NumLock
PageLeft
PageRight
Paste
ScrollLock
Select
Undo
Throughout this guide, descriptions use the keyboard model keys. When the user can use an optional key from the keyboard model, the optional key is also described. Each of the keys described in this model should be available either as specified or by using other keys or key combinations if the specified key is unavailable.
Table 3-1 lists some of the most-often used alternative keys.
Table 3-1. Alternate Keys for Unavailable Specified Keys
| Unavailable Specified Key | Key or Key Combination to Use |
|---|---|
| Cancel | Esc |
| Help | F1 |
| Menu | ShiftF10 |
| F10 | ShiftMenu |
| Begin (and Home, if Home is available) | AltLeft Arrow |
| End | AltRight Arrow |
A pointing device enables the user to move a pointer on the screen and to manipulate interface elements directly. Most keyboard actions can also be accomplished using a pointing device.
The most common pointing device is the mouse; however, a graphics tablet and stylus, pen, track ball, joystick, and other tools are also pointing devices. The model in this book uses the mouse as the pointing device.
The mouse is the most common pointing device and contains one or more buttons with which a user can interact with an application or the operating environment. The actions users perform with the buttons vary depending on the functions assigned to each mouse button. You can map functions to buttons in different ways; therefore, the descriptions in this book actually describe virtual mouse buttons. Button names given when describing a user's action represent either a particular mouse button or a combination of buttons and actions that the user performs to complete a task.
This book uses the following virtual mouse button names:
Left-handed users can switch the mouse buttons to be the reverse of the previous descriptions.
The user can combine the use of the mouse buttons to perform different tasks; this is called a chord. A chord is performed by clicking or pressing two or more mouse buttons (not necessarily simultaneously) so that the buttons have the effect of being pressed at the same time. That is, the user presses one button, holds it down, and then presses another button.
For information about binding application functions to pointing device buttons and about the virtual mouse buttons, see the Mouse (Device) reference page and Appendix C, “Mouse Techniques”.
The following list describes mouse techniques:
Two concepts define how the pointer tracks the motion of the mouse: gain and acceleration.
Gain refers to the ratio of distance the pointer moves to the distance the mouse moves. If the gain is increased, the pointer moves farther for a given mouse movement. The gain remains constant across the environment.
Acceleration refers to a change of gain based on the speed of mouse movements. The user can set the acceleration so that the gain is increased if the mouse is moved quickly, allowing faster pointer movement. If the mouse is moved slowly, the gain is reduced to allow finer pointer position adjustments.
Gain and acceleration are handled on a global scale by the operating system. Unless your application involves user configuration of mouse motion, your application should not change the gain and acceleration characteristics of mouse movement.