Chapter-2 Input and Output Devices

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B Naresh B Naresh B Naresh B Naresh

B Naresh B Naresh B Naresh

B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.

Input and Output Devices

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. Input Devices of a Computer

Input devices:

Data & Instructions are feed into the computer through Input devices. The Input devices convert input data and instructions into binary form which can be understand by the system. We have several types of input devices mainly keyboard and mouse.

I. Keyboard:

The commonly used input device is keyboard. This is connected to CPU and it is used to give the data and instructions into computer. It contains buttons like typewriter keyboard button for alphabets, digits, special characters and some control keys.

Some of important buttons are:

1. Function button:

These are appearing in front line they are starting from F1to F12. These are used to perform specific functions in computer work.

Function keys functionality may change according to package selected by user.

2. Arrow keys:

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. 3. Special keys:

These are used for special purpose.

a. Shift key:

This key is used to get special numbers ( i.e, +,_, &,* etc).

b. Ctrl and Alt:

These keys will work as combination key or short cut keys depending on package.

c. Caps lock:

By using this we can get the capital letters of alphabets.

d. Back space key:

With the help of this key we can erase the data (text) to its left side.

e. Num lock:

This key is useful to activate or deactivate numerical keyboard.

f. Esc key:

This key is used to stop the work in the middle of program.

g. Delete key:

This key is used to delete the letters from the cursor place to its right side.

Advantages

The Keyboard is easy to use and cheap.

Disadvantages

The keyboard cannot be used to draw figures.

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. 2. Pointing Devices

a. Mouse:

Mouse is another basic input device of a computer. It is a pointing device used to move cursor, draw diagrams, selecting a text box/ object/ menu item, etc. on the monitor.

There are different types of mice. They are Mechanical mouse, Optical mouse and wireless mouse.

A mouse which consist a rubber ball is known as mechanical mouse. This ball is moving and controlling the pointer on the screen.

Now a day’s mouse’s are in different models and different sizes. They are as follows;

Mechanical Mouse

A mouse which consists of a rubber ball bottom side of mice is known as Mechanical Mouse. This ball is moving the pointer on the screen. And the rubber ball controls the pointer/ cursor on the flat panel surface or Monitor.

Fig: Mechanical Mouse

Optical Mice/Mouse

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. Cordless Mice/Mouse

Now Wireless (Cordless) Mice are also available, these mice are not connected physically to the computer. These will be worked using radio (including Bluetooth) signals.

b. Track ball:

This is also works like mouse but the little difference is the ball is on top. The finger movements of our hand make movements of the pointer on the screen.

Ex: The most of uses in games.

c. Track pad (or) Touchpad

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. 3. Handheld Devices

a. Pen or Stylus

A stylus is a pen-shaped input device used to enter information or write on the touch screen of handheld device.

b. Joy stick:

It is used in video games. Joy stick controls the cursor movements with the help of digital signal. It is just like a track ball or mouse.

c. Touch screen:

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. 4. Optical Devices

Scanner:

A scanner is another type of input device which is used to read documents, images, graphics, photographs and any other information. The data to be scanned must be on paper. It is just like a small size Xerox machine. In this scanned matter can be stored in computer memory.

Types of Scanners:

Optical character recognition (OCR):

Optical mark reading (OMR):

Magnetic ink character recognition (MICR):

a. Optical character recognition (OCR):

An optical scanner is a device used to read an image, convert it into a set of 0s and 1s and store this in computer’s memory. The image may be a handwritten document, a type or a printed document or a picture. Assume that the image drawn on a graph sheet. If the image drawn over an intersection of horizontal and vertical line of the graph the image is represented by a 0. If not it is represented by a 1.

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.

b. Optical mark reading (OMR):

We have seen special marks such as squares, circles on examination answer sheets in competitive exams. The candidate fills the answers with soft pencils. These answers are detected by OMR and the signals are sending to the processor. The change in the amount of reflected light is used to detect the presence of mark. OMR is used where one out of few alternatives is to be selected.

c. Magnetic Ink character Recognition (MICR):

In this method, human readable characters are printed on the documents (such as cheques) using a special magnetic ink. A magnetic ink character reader can recognize such characters. In a cheque, for instance, the cheque number and branch code are preprinted on the bottom of the cheque using magnetic ink. The amount written in the cheque is later entered by clerk using a machine which prints the amount with magnetic ink.

This method eliminates the need to manually enter the data form cheques. Besides saving time, this method ensures accuracy of data entry.

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. Output Devices of a Computer

Output Devices:

In order to get results from the computer the output devices are useful tools. They are following types. The output devices are classified as follows

Soft copy devices

Soft copy devices produce an electronic version of output. For example, a file that is stored on a hard disk, CD or pen drive and is displayed on the computer screen (monitor).

1. Monitor:

The computer shows the results of our input on the screen. The screen in computer terminology is called a monitor. It is called visual display unit (VDU). It is just like face of computer.

Monitors come in three variants

Cathode Ray Tube (CRT)

Liquid Crystal Display (LCD)

Plasma Monitor.

Cathode Ray Tube

CRT monitors work by firing charged electrons at a phosphorus film. When electrons hit the phosphorus coated screen, they glow, thereby enabling the user to see the output.

Advantages

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CRT monitors are cheapest when compared to LCD and plasma monitors.

Disadvantages

CRT monitors occupy a large space on the desk.

Power consumption is higher than the other monitors.

LCD Monitor

An LCD monitor is a thin, flat, electronic visual display unit that uses the light modulating properties of liquid crystals, which do not emit light directly. LCD technology is based on the principle of blocking light.

Advantages

LCD monitors are very compact and light weight.

They consume less power.

They are more reliable than CRT monitors.

They can be made in almost any size or shape.

Disadvantages

They are expensive that CRT monitors.

Images are not very clear when tried to view from an angle.

Plasma Monitor

These monitors are thin and flat monitors widely used in televisions and computers. The plasma display contains two glass plates that have hundreds of thousands of tiny cells filled with xenon and neon gases.

Advantages

Very bright images are formed which look good from almost every angle.

These monitors are not heave and are thus easily portable.

Disadvantages

These monitors are very expensive.

They consume much power.

2. Projectors

A projector is a device that takes an image from a source and projects it onto a screen or another surface.

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.

a. LCD projector: LCD projectors make use of their own light to display the image on the

screen. These projectors based on LCD technology. To use these projectors, the room must be first darkened, else the image formed will be blurred.

b. Digital Light Processing (DLP) projector: DLP projectors use a number of mirrors to

reflect the light. When using the DLP projector, the room may or may not be darkened.

3. Speakers

Speakers are one of the most common output devices used with computer systems. Some speakers are designed to work specifically with computers, while others can be hooked up to any type of sound system. Regardless of their design, the purpose of speakers is to produce audio output that can be heard by the listener.

Hard copy devices

Hard copy output devices produce a physical form of output. For example, the content of a file printed on paper is a form of hard copy output.

1. Printers:

Printers are the most commonly used output devices that can found in almost all computer centers. They are primary output devices used to prepare permanent documents on paper in human readable form (known as hard copy).

There are different types of printers that are designed for different types of applications. Printers are classified depending on their speed and approach of printing.

Impact Printers

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. Impact Printers:

An Impact Printer creates an image on paper by using pins or hammers to press an inked ribbon against the paper. A simple example of an impact printer is a typewriter, which uses small hammers to strike the ribbon.

Advantages of Impact printers

These printers enable the user to produce carbon copies.

They are cheap.

Disadvantages of Impact printers

Impact printers are slow.

They offer poor print quality.

They can be extremely noisy.

These printers are of two types.

Character Printers

These printers print one character at a time. These printers can be further classified into two types- Daisy Wheel Printer and Dot Matrix printer.

Daisy wheel Printer:

In daisy wheel approach, wheel has a character on it. A motor spins the wheel a rapid speed. When designed character spins to the correct position paper strikes it to produce the output.

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. Dot Matrix Printer:

In early of days, the dot matrix printers were the most commonly used printing devices. Dot Matrix printers are commonly used in workplaces where physical impact with the paper is important.

Dot Matrix Printers are faster than daisy wheel printer, but the quality of Dot Matrix printers are not good compared to daisy wheel printer.

Speed of a dot matrix is measured in the form of characters per second. The speed of Dot Matrix Printer can be up to 360 cps (Characters per Second)

Line Printers:

Line Printers use impact methods to produce a line at a time. The speed is measured in the form of lines per minute. The quality of printing is not good as that of daisy wheel printer.

These are two types- Drum Printers and Chain Printers

Drum Printers:

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E. Chain Printers:

These printers print the line by a rotating chain having ring of characters for each print position. Their printing mechanism is similar to drum printers.

Non-Impact Printers:

Non impact printers do not hit or impact a ribbon to print. They use thermal, electrostatic, chemicals, and Inkjet technologies. These printers print a page at a time, therefore, called as Page Printers.

Advantages of Non-Impact printers

Non-impact printers produce prints of good quality.

They are noiseless.

They are fast.

Disadvantages of Non-Impact printers

These printers are expensive.

The ink cartridges used by them are also costly.

The Non-Impact printers are of two types.

Laser Printer

Laser printer using non impact methods, in these printers a laser beam is used to write the image on a paper.

This type of printer uses fine powder ink called toner. This printer also produces high quality text and graphics on the paper.

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B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.B Naresh B Naresh Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.Department of Computer Science, B.V.R.I.C.E.

Ink jet printer:

These printers print the text and graphics by spraying the paper with electrically charged ink. Inkjet printers produce high quality text and graphics better than character printers but not better than laser printers. They are cheaper than the laser printers, hence used widely in many offices. This printer can print 4 to 6 copies in a minute.

2. Plotter:

A plotter is an output device used to produce hard copies of graphics and design.

Plotters are commonly used for map printing, engineering designs etc. plotters are normally very slow in motion because of excessive mechanical movement.

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Important Questions

1. Explain various Input Devices of a Computer.

2. Explain different types of Scanners.

3. Explain various Output Devices of a Computer.

4. Explain types of Monitors.

Figure

Fig: Mechanical Mouse  Optical Mice/Mouse
Fig: Mechanical Mouse Optical Mice/Mouse p.4

References