Input Devices of Computer Systems- Part 1(Keyboard & Point-and draw devices)

INPUT DEVICES OF COMPUTER SYSTEMS

An input device is an electromechanical device, which collects data from the outside world, and free translates into computer useable form, which the computer can interpret. Several input devices are available today. They are-

1. Keyboard devices

2. Point-and draw devices

3. Data scanning devices.

4. Digitizer

5. Electronic cards based devices

6. Voice recognition devices

7. Vision-based devices

             The various types of input devices along with their typical applications are described (Keyboard & Point-and draw devices) below.

1.  Keyboard Devices:

             Keyboard devices are the most commonly used input devices today. They allow data entry into a computer system by pressing a set of keys (labeled buttons), which are nearly mounted on a keyboard, which connected to the system.  The most popular keyboard used today is the 101-keys QWERTY keyboard. It is shown in Figure1.

 2.   Point-and-Draw Devices:

             Interaction with computers was initially restricted mainly to text mode. However, it was soon realized that interacting with computers in text –mode is cumbersome and time-consuming. Hence, a new type of interface, called graphical user interface (GUI), was devised for interacting with computers. As shown in Figure-2, a GUI provides a screen full of graphic icons (small images on the screen) or menus to the user make a rapid selection from the displayed icons or menus to give instructions to the computer. With such a user interface, the basic requirement is to have the an input device, which can be used to rapidly point to and select a particular graphic icon or menu item from the multiple options displayed on the screen.

The keyboard was found to be very inconvenient, and unsuitable for this requirement. Hence, research efforts to find a suitable input device to meet this requirement, gave birth to several input devices like mouse, track ball, joystick, light pen and touch screen. Later was realized that many of these devices, like mouse and light pen, could also be very effectively used to create graphic elements on the screen, such as lines, curves and freehand shapes. With this new ability these devices came to be known as point-and-draw devices. These input devices have made computers a much more easily usable tool, and have established the computer as a versatile tool for graphic designers. Some of the most commonly used point–and-draw devices are described below.

 2.1 Mouse:

             Today, mouse is the most popular point-and-draw device. It has become a    most essential input device on personal computers and workstations, which have a GUI based user interface. As shown in Figure 2.1, a mouse is a small hand-held device, which can comfortably fit in a user’s palm. It rolls on a small bearing, and has one or more buttons, on the top. When a user rolls the mouse across a flat surface, such as on the top of the table on which the computer is placed, the graphics cursor moves on the screen of the video display terminal in the direction of the screen of the mouse’s movement. The graphics cursor, which is used to point and draw, is displayed on the screen as a variety of symbols, such as an arrow a wrist with a pointing finger etc.

 Depending on the application, the text and graphics cursor may be displayed on the screen at the same time. Since all movements of the mouse are reproduced by the graphics cursor on the screen, you can move the graphics cursor at a menu item or an icon by moving the mouse. For example, move the mouse from you to move the cursor up on the screen, move the mouse towards you to move the cursor down on the screen, move the mouse right to move the cursor right on the screen, and move the mouse left to move the cursor left on the screen. In this way, the mouse can be used for quick positioning of the graphics cursor on the desired menu item or an icon. When positioned at a menu item or icon, the graphics cursor is said to point to that menu item or icon. With a click of the mouse’s button, the system can then be notified of this choice. Note that, notifying the system of a particular choice, out of the various options provided by the software, is much easier with a mouse than pressing various key combinations. With the proper software, a mouse can also be used to draw picture on the screen and edit text.

 2.2 Trackball

             A trackball is a pointing device, which is similar to a mouse. As shown in Figure 2.2 the ball, which is the base of a mouse, is place Magnetic-Ink Character Recognition (MICR) on the top along with the buttons, in case of a trackball. To move the graphics cursor around the screen, the ball is rolled with the fingers, Because the whole device is not moved for moving the graphics cursor, a trackball requires less space than a mouse for operation. Since it need not be moved for moving the graphics cursor, it is often attached to or built into the keyboard. Trackballs build into the keyboard are commonly used in laptop (notebook) computers, because a mouse is not practical for laptop users in a small space because the ball is fixed on the top, some people find it helpful to think of a trackball as an upside-down mouse.

  A trackball comes in various shapes and forms with the same functionality. Three commonly used shapes are a ball, a button, and a square. In case of a ball the ball is rolled with the help of fingers to move the graphics cursor. In case of a button, the button is pushed with a finger in the desired direction of the graphics cursor movement. In case of a square plastic, the finger is placed on top of it, and moved in the desired direction of the graphics cursor movement.

 2.3 Joystick

             A joystick is a pointing device, which works on the same principle as a trackball. To make the movement of the spherical ball easier, the spherical ball, which moves in a socket, has a stick mounted on it (see Figure 2.3). Instead of using the fingers in case of a trackball, the user of a joystick moves the spherical ball with the help of the stick with his/her hand.

The stick can be moved forward or backward, left or right, to move and position the graphics cursor at the desired position. Potentiometers are used to sense the movements. On most joysticks, a button on the top is provided to select the option, which is currently pointed to by the cursor. The button is clicked to make this selection. Typical uses of a joystick include video games, flight simulators, training simulators, and for controlling industrial robots.

 2.4 Electronic pen

             Another point-and-draw device is an electronic pen.

    In a pen-based system, you hold the pen in your hand, and directly point with it on the screen to select menu items or directly draw graphics on the screen with it; or write with it on a special pad for direct input of the written information to system.

 2.5 Touch screen

             Touch screen is the most simple, intuitive, and easiest to learn of all devices. A touch enables the users to choose from available options by simply touching with finger the desired icon or menu item displayed on the computer’s screen. Figure 2.5 shows a touch screen computer display.

Touch screens are the most preferred human-computer interface devices used in information kiosks. An information kiosk is an unattended system, which is used to store information of pubic interest, and allows common people to access the stored information as per their requirement. For example, information kiosks may be located

 1. At an airport or a railway station to provide information to arriving passengers about hotels, restaurants, tourists spots, etc. in the city.

 2. In large museums or zoos to guide the visitors to locations and facilities, and to caution them against things, which they are not supposed to do while inside.