Input And Output Devices
Pointing devices: pointing devices control the position of the cursor or pointer on the screen. They include the following:
- Mouse
- Trackball
- Pointing stick
- Touch pad
- Touch screen
- Light pen
- Digitizing/ graphic tablet
- Pen-based system
A brief description is given as under:
Mouse:
a mouse is an input device that device that looks a little bit like a mouse. It has a ball on its underside that is rolled on a flat surface or mouse-pad. The rolling movement causes a corresponding cursor movement on the screen. It enables us to reposition the cursor (or pointer) on the screen where ever we want. It also has buttons on its top which communicate certain commands to the computer while pressed. In particular, button is often used to click on an icon(icon represents a computer activity or command) to invoke the command.
Trackball:
The trackball is a movable ball, on top of a stationary device, that is rotated with fingers or palm of the hand. Its popularity surged with the advent of laptop computers where traveling users found themselves without a flat surface to roll the traditional mouse. It looks like the mouse turned upside down and likewise, has additional buttons whose functions vary depending on the software.
Pointing stick
A pointing stick is a pointing device that looks like a pencil eraser protruding from the keyboard between the G, H, and B keys. we move the pointing stick with our forefinger while using the thumb to press buttons located in front of the space bar. Another device like a pointing stick is the joystick, it is a pointing device that consists of a vertical handle like a gearshift lever mounted on a base with one or two buttons. It is basically used in video games lever mounted on a base with one or two buttons. It is basically used in video games and in some computer-aided design systems.
Touch pad
The touch pad is a small, flat surface over which we slide our finger, using the same movements as we would with a mouse. As we move the finger, the cursor follows the movement. We “click” by tapping the finger on the pad’s surface or by pressing button positioned close by the pad. Touch pads are now common on the portable computers (laptops).
Touch Screen
A touch screen is a video display screen that is sensitized to receive input from simply touching our fingers onto it. It is covered with a plastic layer, behind which are invisible beams of infrared light. We simply touch the provided buttons or menus and get the information on the display screen accordingly.
Light Pen
The light pen is a light-sensitive stylus, or pen-like device, connected by a wire to the computer terminal. The user brings the pen to a desired point on the display screen and presses the pen button, which identifies that screen location to the computer. Engineers, graphic designers, and illustrators use light pens.
Digitizing/Graphic Tablet
A digitizing tablet consists of a tablet connected by a wire to a stylus is a pen-like device with which the user copies an image, such as an architectural drawing or a civil engineering map. A puck looks a bit like a mouse but has different types of buttons and a clear plastic section extending from one end with crosshairs printed on it. The intersection of the crosshairs points to a location on the graphics tablet, which in turn is mapped to a specific location on the screen.
Digitizing tablets are used primarily in design and engineering. When used with drawing and painting software, a digitizing tablet and stylus allow us to do shading and many other effects similar to those artists achieve with pencil, pen, or charcoal. Alternatively, when we use a puck, we can trace a drawing laid on the tablet, and a digitized copy is stored in the computer.
Pen-Based Systems
In the next few years, students may be able to take notes in class without ink and paper, if pen-based computer systems are introduced. These computers use a pen-like stylus to allow people to enter handwriting and marks onto a computer screen rather than typing on a keyboard. This system connects an instructor’s electronic “ whiteboard” on the classroom wall with student’s pen computers, so that the students could receive notes directly, without having to copy information word for word. “ the idea is that the students should concentrate on the lecture listening only”.
