INPUT OUTPUT AND STORAGE DEVICES

Peripheral is the generic name given to all input/output equipment and secondary storage devices that depend on direct connections or telecommunications links to the central processing unit of a computer system. Thus, all peripherals are online devices; that is, they are separate from, but can be electronically connected to and controlled by, a CPU. (This is the opposite of offline devices, which are separate from and not under the control of the CPU. ) The major types of peripherals and media that can be part of a computer system are discussed in this section.

Computer Terminal Trends. The most common user interface method still involves keyboard for entry of data and a video display screen for output to users. Computer terminals < various types are widely used for such input and output. Technically, any input/output devic connected by telecommunications links to a computer is called a terminal. However, moi terminals use a keyboard for input and a TV-like screen for visual output, and are called vism (or video) display terminals (VDTs) or, more popularly, CRT (cathode ray tube) terminals They allow keyed-in data to be displayed and edited before entry into a computer system.

There is a trend away from dumb terminals, which have no processing capabilitie: themselves, toward intelligent terminals, which have their own microprocessors and memorj circuits. Many intelligent terminals are really microcomputers used as telecommunication! terminals to larger computers. Therefore, they can perform data entry and other information processing tasks independently. Another trend is the widespread use of transaction terminals in banks, retail stores, factories, and other work sites. Examples are automated teller machines (ATMs), factory transaction recorders, and retail point-of-sale (POS) terminals. These terminals use a variety of input/output methods to capture data from end users during a transaction and transmit it over telecommunications networks to a computer system for processing.

Keyboards are the most widely used devices for entering data and text into computer systems. However, pointing devices are a better alternative for issuing commands, making choices, and responding to prompts displayed on your video screen. For example, pointing devices such as electronic mice and trackballs allow you to easily choose Replica Omega Speedmaster from menu selections and icon displays using point-and-click or point-and-drag methods. Icons are small figures that look like familiar devices, such as a file folder (for accessing a file), a wastebasket (for deleting a file), a calculator (for switching to a calculator mode), and so on. Using icons helps simplify computer use since they are easier to use with pointing devices than menus and other text-based displays.

The electronic mouse is a device used to move the cursor on the screen, as well as to issue commands and make icon and menu selections. Some mice contain a roller ball, which moves the cursor in the direction the ball is rolled. Others use an optical sensing technology that recognizes points on a special pad. By moving the mouse on a desktop or pad, an end user can move the cursor onto an icon displayed on the screen. Pressing a button on the mouse begins the activity represented by the icon selected.

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