On-line or Direct Data Entry Devices: These devices are under the control of the CPU and communicate directly with the CPU, that is, these are connected via cable to the CPU. This process of data entry may be time consuming and may have errors but by using these devices, we can avoid having to capture data from paper. These are also known as Interactive Input Devices and are classified as:
(a) Keyboard
(b) Locator devices
(c) Interface or pick devices.
(a) Keyboard
The most common input device is the keyboard. The modern keyboard generally contains 104 keys and is called the QWERTY keyboard because of the sequence of keys in the top row, which are similar to those of a standard typewriter. A keyboard is used for a wide range of tasks but is well known for its capability to enter data, which is copied from the original paper documents (such as name and address details on a form). Keyboards are also used for typing letters, memos, reports and other documents using word processing software enter data, which is copied from the original paper documents (such as name and address details on a form). Keyboards are also used for typing letters, memos, reports and other documents using word processing software.
(b) Locator devices
Locator devices are used to control the location or position of the cursor on the screen and they allow us to provide the necessary input. Generally, locator devices are good for gross movement but not for precision work. Different locator devices are Mouse, Trackball, Touch pad, Digitising Tablet and Joystick.
(c) Interface/Pick Devices
Pick devices are used to select an object on the screen. The object may be text or graphic. Examples of pick devices are light pens and touch screens.
Light Pens: The light pen is a pen-like light-sensitive device that feeds a narrow electrical pulse generated by a pointing device directed towards the screen. It is connected by a wire to the computer terminal that detects the signals from the screen. Light pens may be used in place of a mouse or a keyboard, particularly for menu based applications where an option may be selected by pointing on it. They are used for Computer Aided Designing (CAD) and drawing purposes. Moreover, with the help of a light pen, engineers, architects or fashion designers can draw and edit the designs directly on the screen, though for editing a drawing keyboard may be used to select colours, lines with varying thickness, cropping or enlarging the drawings. It is also used to read bar codes from products that are available in big departmental stores.
Touch Screens: Touch screens are monitors on which the user makes selections by touching the screen, rather than moving a cursor to the location with external locator devices.
Touch screens are often used in situations where users are likely to have a low level of competence in using computer keyboards. Touch screens are sometimes used in restaurants, building societies and travel information systems.
