An input device is a hardware mechanism that transforms information in the external world for consumption by a computer. Often, input devices are under direct control by a human user, who uses them to communicate commands or other information to be processed by the computer, which may then transmit feedback to the user through an output device. Input and output devices together make up the hardware interface between a computer and the user or external world. Typical examples of input devices include keyboards and mice. However, there are others which provide many more degrees of freedom. In general, any sensor which monitors, scans for and accepts information from the external world can be considered an input device, whether or not the information is under the direct control of a user.
History
A definition of an input device was already included within the von Neumann architecture in 1945, however conception of an architecture including similar devices designed for input only appear since 1936. The von Neumann architecture describes a device designed for inserting user data, which are separated from the algorithm data and code. These devices included a keyboard or a punched card.
Mice were invented by Doug Engelbart in the 1960s.
Classification
Many input devices can be classified according to:-
- the modality of input (e.g. mechanical motion, audio, visual, sound, etc.)
- whether the input is discrete (e.g. keypresses) or continuous (e.g. a mouse's position, though digitized into a discrete quantity, is high-resolution enough to be thought of as continuous)
- the number of degrees of freedom involved (e.g. many mice allow 2D positional input, but some devices allow 3D input, such as the Logitech Magellan Space Mouse)
Pointing devices, which are input devices used to specify a position in space, can further be classified according to
- Whether the input is direct or indirect. With direct input, the input space coincides with the display space, i.e. pointing is done in the space where visual feedback or the cursor appears. Touchscreens and light pens involve direct input. Examples involving indirect input include the mouse and trackball.
- Whether the positional information is absolute (e.g. on a touch screen) or relative (e.g. with a mouse that can be lifted and repositioned)
Note that direct input is almost necessarily absolute, but indirect input may be either absolute or relative. For example, digitizing graphics tablets that do not have an embedded screen involve indirect input, and sense absolute positions and are often run in an absolute input mode, but they may also be setup to simulate a relative input mode where the stylus or puck can be lifted and repositioned.
Early devices
Keyboards
Examples of types of keyboards include
Issues and techniques related to keyboards include
- Keyboard shortcut
- Command history
- Autocomplete
- Autoreplace
- Intellisense
- ShapeWriter
- Chinese input methods for computers
Pointing devices
A pointing device is any computer hardware component (specifically human interface device) that allows a user to input spatial (ie, continuous and multi-dimensional) data to a computer. CAD systems and graphical user interfaces (GUI) allow the user to control and provide data to the computer using physical gestures - point, click, and drag - typically by moving a hand-held mouse across the surface of the physical desktop and activating switches on the mouse. Movements of the pointing device are echoed on the screen by movements of the mouse pointer (or cursor) and other visual changes.
While the most common pointing device by far is the mouse, many more devices have been developed. However, mouse is commonly used as a metaphor for devices that move the cursor.
For most pointing devices, Fitts' law can be used to predict the speed with which users can point at a given target position.
Examples of common pointing devices include
- mouse
- trackball
- touchpad
- spaceBall - 6 degrees-of-freedom controller
- touchscreen
- graphics tablets (or digitizing tablet) that use a stylus
- light pen
- light gun
- eye tracking devices
- steering wheel - can be thought of as a 1D pointing device
- yoke (aircraft)
- jog dial - another 1D pointing device
- isotonic joysticks - where the user can freely change the position of the stick, with more or less constant force
- isometric joysticks - where the user controls the stick by varying the amount of force they push with, and the position of the stick remains more or less constant
- discrete pointing devices
- directional pad - a very simple keyboard
- dance pad - used to point at gross locations in space with feet
High-degree of freedom input devices
Some devices allow many continuous degrees of freedom to be input, and could sometimes be used as pointing devices, but could also be used in other ways that don't conceptually involve pointing at a location in space.
- Wired glove
- ShapeTape: [1]
- Some haptic devices
Composite devices
Input devices, such as buttons and joysticks, can be combined on a single physical device that could be thought of as a composite device. Many gaming devices have controllers like this.
Imaging and Video input devices
- Webcam
- Image scanner
- Fingerprint scanner
- Barcode reader
- 3D scanner
- medical imaging sensor technology
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