Keyboard: Keyboard is the most commonly used input device. Data is mostly entered using a keyboard. The buttons on the keyboard are called keys. A standard keyboard contains over 100 keys. A keyboard contains numeric keys, alphabetic keys, function keys and special – purpose keys. A standard keyboard is normally called QWERTY keyboard. This is because the first six keys on the top row of letters on these keyboards are Q,W,E,R,T,Y.
Main Parts of Keyboard
The keyboard in most personal computers have the following main parts:
1. Function Keys 2. Main Keyboard (in the center)
3. Numeric Keys (to the right) 4. Additional Keys
1. Function Keys
Function keys from F1 to F12 are used to perform special functions. Their function depend on the software being used in the computer.
2. Main Keyboard
The main keyboard includes the keys found on a typewriter keypad. It also contains some special keys. The special keys have different uses and effects that depend on the software being used.
101 – Key Enhanced Keyboard
101 – key enhanced keyboard has some additional keys between the main keypad and the numeric keys. It also contains status lights in upper – right corner.
a) Esc Key
ESC key is used to terminate a command or current task.
b) CapsLock Key
CapsLock is a toggle key. The characters appear in uppercase if it is pressed. The characters appear in lowercase if it is not pressed. Numbers and symbols are not affected. The status light under “CapsLock” turns on when it is pressed.
c) Tab Key
Tab key is used to move the cursor to next tab stop.
d) Shift Keys
Shift key is pressed in combination with other keys to produce upper case letters and the upper symbols shown on certain keys.
Figure: 101 – key Enhanced keyboard
e) Control Keys
Control key is pressed in combination with other keys to execute commands. For example, CTRL+O is used to open a new file.
f) Alt Keys
ALT key is also used in combination with other keys to execute commands.
g) Backspace Key
Backspace key is used to delete single character on the left of the cursor.
h) Enter Key
Enter key is used to move the cursor to the beginning of the next line. It is normally used at the end of a paragraph.
3. Numeric Keys
Numeric keys are located on the right side of most keyboards. The numeric keys are used for two purposes depending on the status of NumLock key. If NumLock is on, the keys are used to enter numeric data and mathematical symbols like +, -, *, /. If NumLock key is off, the numeric keys are used to move the cursor and perform other functions as follows:
1. Additional Keys
Some additional keys on extended keyboard are as follows:
• Arrow Keys: The arrows keys are used to move the cursor position.
• Insert, Delete, Home, End, Page up and Page Down keys: These keys are above the arrows key. The function of these keys are same as numeric keys 0, decimal point (del), 7, 1, 9, and 3.
• Print Screen: It is used to take a snap of the computer screen.
• Scroll Lock: It locks and unlocks the cursor on screen in some programs. The cursor moves normally when it is turned off. It does not work in all programs.
• Pause or Break Key: It is used to pause screen when information is too fast to read.
Q. What are pointing devices? List the names of different pointing devices.
An input device used to control a pointer on the screen is called pointing device. A pointer is a small symbol that appears on the screen in graphical user interface.
Some important pointing devices are as follows:
• Mouse • Trackball • Pointing Stick
• Touch Pad • Touch Screen • Light Pen
• Digitizer / Graphic Tablet • Joystick • Pen – based System
Q. What is mouse? Describe its function.
Mouse is the most widely used pointing device. It is a small and lightweight input device. Mouse is moved on a flat surface to control the movement of the cursor or pointer on a screen. It is attached to the computer by a cable or wireless connection. Mouse is very easy to use. It is mostly used in graphics applications.
A mouse usually has two or three buttons. These buttons are used to perform different tasks. It may also include a scroll wheel to scroll through long documents. The mouse contains a small ball at the bottom. The movement of the cursor depends on the movement of ball.
Q. Briefly describe track ball.
A trackball can be used as an alternative to a mouse. This device has buttons similar to those on mouse. It has a large rotating ball on the top. The body of the track ball is not moved. The ball is rolled with fingers. The position of the cursor on the screen is controlled by rotating the ball.
An advantage of the trackball is that it takes less space to move than mouse. Trackball is often included in laptop computers. It can also be used as separate input devices with standard desktop computers.
Q. What is the purpose of touch pad / track pad?
A touch pad also has one or more buttons near it. These buttons work like mouse buttons. Touch pads are commonly used with notebook computer.
Q. Describe touch screen.
Touch screen is a video display screen that receives that receives input from the touch of finger. The screen is covered with a plastic layer. There are invisible beams of infrared light behind the screen. The user enters data by touching icons or menus on the screen. Most touch screen computers use sensors to detect touch of a finger. Touch screen is commonly used in ATM, departmental stores and supermarkets.
Q. Briefly explain pointing stick.
Pointing stick is a pressure – sensitive device. It is similar to a pencil eraser and exists between keys on the keyboard. The pointer on the screen moves when the user pushes the pointing stick. It requires no additional space or cleaning like mouse. Pointing stick is normally used with notebook computers.
Q. What is digitizer / graphics tablet?
A graphics tablet consists of a flat pad connected to a stylus or puck by wire. A stylus is a pen – like device used to create sketches and images. A puck is a copying device used to copy an image. A puck looks like a mouse. The puck is specially used to trace a drawing and store it in the computer in digital form.
A designer can produce very accurate drawings using graphics tablet. Graphic tablets are often used to make maps and engineering drawings.
Q. Briefly describe light pen.
A light pen is a hand held pointing device. It looks like a pen. It is connected by a wire to the computer. The pen sends information to the computer when user touches the pen on specific areas of a specially designed screen. Light pen is usually used by engineers and graphic designers etc.
Q. Explain the purpose of joystick.
A joystick consists of a base and a stick. The stick can be moved in any direction to move an object around the computer screen. A joystick can perform a similar function to a mouse or trackball. But it is often considered less comfortable and efficient. The most common use of a joystick is for playing computer games.
Q. Describe the pen – based computer systems.
Pen – based system is used to enter handwriting and marks in computer using pen – like stylus. The user writes words and symbols on the screen. This system uses handwriting recognition software. The software translates handwritten characters into a form that can be stored and processed by computer. Many handheld computers have pen input. Pen – based systems are commonly used to input signatures or messages that are stored as images.