Input/Output Devices

Topics: Computer keys, Input device, Computer-aided design Pages: 6 (1556 words) Published: August 15, 2012
Chapter 9 Input/Output Devices
I. Introduction II. Input Devices a. Keyboard,mouse,joystick,scanners,digital camera, bar code reader, touch Sreeen,Speech input device (microphone) III. Output Devices a. Monitor , Speaker, Printers ( different types) ----------------------------------------------------------------------------------------I. Introduction The computer will be of no use unless it is able to communicate with the outside world. Input/Output devices are required for users to communicate with the computer. In simple terms, input devices bring information INTO the computer and output devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system. Some commonly used Input/Output devices are listed in table below.

Input Devices Keyboard Mouse Joystick Scanner Light Pen Touch Screen

Output Devices Monitor LCD Printer Plotter

II. Input Devices
(a) Keyboard It is a text base input device that allows the user to input alphabets, numbers and other characters. It consists of a set of keys mounted on a board.


Alphanumeric Keypad/ Special-function Keys

Function Keys Cursor Movement Keys

Numeric Keypad

Figure 1: The Keyboard

Alphanumeric Keypad It consists of keys for English alphabets, 0 to 9 numbers, and special characters like + − / * ( ) etc. Function Keys There are twelve function keys labeled F1, F2, F3… F12. The functions assigned to these keys differ from one software package to another. These keys are also user programmable keys. Special-function Keys These keys have special functions assigned to them and can be used only for those specific purposes. Functions of some of the important keys are defined below. Enter It is similar to the ‘return’ key of the typewriter and is used to execute a command or program. Spacebar It is used to enter a space at the current cursor location. Backspace This key is used to move the cursor one position to the left and also delete the character in that position. Delete It is used to delete the character at the cursor position. Insert Insert key is used to toggle between insert and overwrite mode during data entry. Shift This key is used to type capital letters when pressed along with an alphabet key. Also used to type the special characters located on the upper-side of a key that has two characters defined on the same key. Caps Lock Cap Lock is used to toggle between the capital lock features. When ‘on’, it locks the alphanumeric keypad for capital letters input only.

Tab Tab is used to move the cursor to the next tab position defined in the document. Also, it is used to insert indentation into a document. Ctrl


Control key is used in conjunction with other keys to provide additional functionality on the keyboard. Alt Also like the control key, Alt key is always used in combination with other keys to perform specific tasks. Esc This key is usually used to negate a command. Also used to cancel or abort executing programs. Numeric Keypad Numeric keypad is located on the right side of the keyboard and consists of keys having numbers (0 to 9) and mathematical operators (+ − * /) defined on them. This keypad is provided to support quick entry for numeric data. Cursor Movement Keys These are arrow keys and are used to move the cursor in the direction indicated by the arrow (up, down, left, right). (b) Mouse The mouse is a small device used to point to a particular place on the screen and select in order to perform one or more actions. It can be used to select menu commands, size windows, start programs etc. The most conventional kind of mouse has two buttons on top: the left one being used most frequently. Mouse Actions Left Click : Used to select an item. Double Click : Used to start a program or open a file. Right Click : Usually used to display a set of commands. Drag and Drop : It allows you to select and move an item from one...
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