Output Devices

OUTPUT DEVICES

Output devices enable us to perceive the results of computer processing- to see these results, to hear them, and even to feel them. There are many types of output devices like monitor, speaker, plotters, printers, etc.

1. MONITORS

Monitors also called as displays or VDU displays the video adapter’s output. The on-screen display enables us to see how applications are processing our data, but it’s important to remember that the screen display isn’t permanent record. To drive home this point, screen output is sometimes called softcopy since we can only feel it and not touch it. There are two types of monitors in the market. They are:

a) CRT Monitors

CRT Monitor

CRT(Cathod Ray Tubes) monitors are like our commonly used television set in our home which consists of electron gun which fires electrons rapidly which passes through magnetic coil and strikes the phosphorus coated screen and the coated starts to glow forming image on it. There are again two types of CRT Monitors. They are:

Color CRT Monitor

i. Monochrome CRT Monitors

They have only one electron gun present for producing black and white colors.

ii. Color CRT Monitors

They have three electron guns present for producing RGB (Red, Green and Blue respectively) Colors.

b) Flat Panel Monitors

Flat Panel Monitors

A flat Panel monitor is smaller in size. They are highly portable and consumes less power but images produced in flat panel are less bright the CRT monitors which makes it safe for our health point of view. They are also more expensive than CRT monitors. They are classified on the basis of the substance used. On the basis of substance used, they are classified into three types of monitors which are:

i. LCD Monitors (Liquid Crystal Display)

LCD Monitor

In LCD monitors, liquid substance is used in between the two plates. This liquid becomes opaque when charged with the electricity and image is formed.

ii. ELD Monitors( Electrolumincient Display )

In ELD monitors, solid substance is used in between the plates. This solid substance starts to glow when charge with the electricity and image is formed in the screen.

iii. Gas Plasma

In Gas Plasma monitor, gas substance is used in between the plates. This gas substance starts to glow when charge with the electricity and image is formed in the screen.

2. PLOTTERS

Plotters is specialized hard copy output device which can produce high quality graphics. Specially, plotters are designed for producing high quality map and architectural drawing.

On the basic of working principle, plotters can be divided into three types.

 They are:

Pen Plotter

a. Pen Plotters

Pen Plotters may consist 1 to 4 pens having different color(s). At the bottom the pen(s) a flat of paper is moved to plot on the paper. This plotter can produce up to 4 colors.

b. Electrostatic Plotters

Electrostatic plotters use electrostatic charges to produce tiny dots on a specialized paper. When a paper is run through the developer, a image is produced on the paper. It is also capable of producing 4 colors.

Thermal Plotter

c. Thermal Plotters

Thermal Plotters consists of heated heads and a special type of heat sensitive paper when the heated heads are moved on the paper, image can be plotted on the paper. This plotter is capable of producing 2 colors.

3. VOICE RECOGNITION UNIT

Computer equipped with sound card can accept sound input from a microphone. The sound card translates digital sounds into the electric current that is sent to the speakers. Sound cards are essential for multimedia computers with CD-ROMS which has become common on all personal computers.

Sound Card

In PCs, a sound card is an expansion board designed to record and play back sound files. Sound files contain digitized sound data, which is saved to one of several standardized sound formats. These formats specify how sounds should be digitally represented, and generally include some type of data compression that reduces the size of the file. Examples of popular sound file formats are the Windows WAV format, AU sound (a low quality, monaural sound format often encountered on the Internet), and Motion Pictures Expert Group (MPEG) audio formats (called MP-2 and MP-3). The MPEG formats reduce file size significantly without sacrificing audio quality.

Speaker

Almost all sound cards support MIDI, a standard for representing music electronically. Also, most sound cards are sound blaster-compatible, which means that they can process commands written for a sound blaster card, and I reality it is necessary standard for PC sound.

Sound cards use two basic methods to translate digital data into analog sounds.

i. Frequency Modulation (FM) Synthesis mimics different musical instruments according built-in formulas.

ii. Wavetable Synthesis relies on recordings of actual instruments to produce sound Wavetable synthesis produce more accurate sound, but is also more expensive.

4. PRINTERS

Printers are one of the main output devices. It gives hard or printed output. The output we get through this device is called as hard copy output. There are different types of printers. They are classified according to the speed and the use of technology. Printers are basically categorized into tow types. They are Impact and Non-Impact Printers.

a. Impact Printers

An impact printer is like a typewriter and the characters are formed by physically striking the type device against an inked ribbon. Impact printers can produce a page, a line, or character at a time.

They can again be classified into two types according to their mechanism. They are:

i. Character Printers: The printer which are able to print a character at a time is known as character printers. Examples of character printers are:

Daisy wheel

1. Daisy Wheel Printer

The print element of Daisy Wheel printer is a flat spoke wheel with characters embossed along the outer edge of the spokes. The daisy wheel print element rotates to the appropriate character which is then struck with a hammer. Most of the word processor use a daisy wheel printer for the output. Type fonts in daisy wheel printer can be changed conveniently by changing the daisy wheel element.

Dot Matrix Printer

2. Dot Matrix

Dot Matrix is the basis of printing mechanism in Dot-Matrix printers. The dot matrix is formed by arranging a number of small rods in a specific number of rows and columns. The number of rows and the number of columns in the dot-matrix may vary from printer to printer. No type elements requires to be shifted in this; in order to print a character it is only necessary to strike the corresponding configuration of rods.

ii. Line Printers

The type of printer that prints a whole line at a time is known as line printer. They are of also two types. They are:

Drum Printer

1. Drum Printer:

The print element is a drum or a cylinder with a complete set of characters engraved of it around the drum. Each band has one each of the different characters and there are as many bands along the cylinder length as the number of characters the printer can print in one line. Each position has its own hammer. To print a character, the drum rotates to the appropriate position and the hammer strikes the paper against the ribbon and the type element.

2. Chain Printer

The print element in a chain printer is a chain that rotates horizontally in front of paper. Several set of characters are located on the chain. As a drum printer hammer are positioned on the other side of the paper. The chain is rotating and when the appropriate printer is one of the fastest impact printers.

b. Non Impact Printers

Non impact printers are the printers that print by spraying ink, by laser beam or by using heat. They are more reliable, faster and quieter than impact printers.

Inkjet Printers

i. Ink Jet Printers

Ink jet printers also called bubble jet printers prints by spraying tiny ink in the paper. It works by forming an image that is composed of tiny dots. Inkjet printers spray small droplets of ink rapidly from tiny nozzles onto the surface of paper to form characters. It can also print in color, which makes it popular choices for home users.

How Laser Printer Works

ii. Laser Printers

Laser printer also known as page printer produce very high quality output of text or data generated from a word processing or a data processing system. It uses laser beam to create the image. Under the printer’s computerized control, a laser beam creates electrical charges on a rotating print drum. These charges attract toner, which is transferred to the paper and fused to its surface by a heat process. In contrast to ink jet, laser printers prints faster, some can crank out18 or more pages per minute.

Thermal Printer

iii. Thermal Printers

Thermal printers use electrical heat to generate an image on specially treated paper. The printer uses pins to produce an image, but rather than striking the pins against a ribbon to mark the paper as does a wire-pin dot-matrix printer, it heats the pins and brings them into gentle contact with the paper. The special coating on the paper discolors when it is heated. The thermal printers are inexpensive and are used in most calculators and fax machines. They produce low quality print and the paper tends to curl and fade after a few weeks or months.

Input Devices

Input Devices:

The medium through which we can feed our data or instructions to the computer to perform several tasks is known as Input Devices. Input Devices are necessary to convert our information or data in to a form which can be understood by the computer.

Types of Input Devices are as follows:

KeyBoard

1. Keyboard

This is the standard input device attached to all computers. The layout of keyboard just like the traditional typewriter of the type QWERTY. It also contains some extra command keys and functions keys. It contains a total of 101 to 104 keys. Combination of keys should be pressed to input data. The computer can recognize the electrical signals corresponding to the correct key combination and processing id done accordingly.

Mouse

2. Mouse

Mouse is an input device that is used with personal computers. It rolls on a small ball and has two or three buttons on the top; When the rolling the mouse across a flat surface the screen censors the mouse in the direction of mouse movement. The cursor moves very fast with mouse giving more freedom to work in any direction. It is easier and faster to move through mouse.

Scanner

3. Scanner

A scanner is and input device that transfers information from a piece of paper into a computer. To do this, the scanner sends a beam of light to the page and then measures the amount light reflected back, white reflects all the light , black reflect not light, ad each color reflects different amount of light. The amount of light for each portion is given a digital code which is sent to the computer. A document is laid face down on the glass. The light moves backwards and forwards.

MICR

4. Magnetic Ink Character Recognition (MICR)

MICR is a form of character recognition that reads text printed with magnetically charged ink, determining the shapes of characters by sensing the magnetic charge in the ink, once the shapes have been determined, character recognition methods are used to translate the shapes into computer text. A familiar use of the is form a of character recognition is to identify bank cheques.

5. Optical Character Recognition (OCR)

OCR

Optical Character Recognition is the ability of a machine to recognize characters. The machine, called a scanner, uses light, or optics, to read text from a piece of paper, special software compares the pattern of the signals sent from the scanner to patterns held in memory. When a match is made, a signal is sent to the computer. Optical character recognition depends on the computer matching two patterns.

OMR

6. Optical Mark Recognition (OMR)

Optical Mark Recognition is a type of input device that reads hand-drawn marks such as small circles or rectangles. A person places these marks on a form, such as a teat, survey or questionnaires, answer-sheet. It can read information in the form of numbers or letters and put in to the computer. The marks have to be precisely located as in multiple choice test papers.

Track Ball

7. Track Ball

A trackball is an input device, another pointing device used to move the cursor. It is a ball which is rotated by the user’s finger. Trackballs may be on the keyboard, or plug into the computer separately. A trackball moves the cursor in the direction the ball is moved.

Joystick

8. Joystick

Joystick is a pointing device, one of the input devices that are used to move the cursor on the screen. It has a stick with balls at its upper and lower ends. We can move the stick in different directions like from left to right to forward or backward. Joystick is mostly used while playing computer games.

9. Digital Camera

Camera

It is a type of camera that stores photographed images electronically instead of on traditional film. A digital camera uses a CCD(Charge-coupled device) element to capture the image through lens when the operator release the shutter in the camera; circuitry within the camera then stores the image captured by the CCD in a storage medium such as solid-state memory or a harddisk. After the image has been captured, it is downloaded by cable to the computer using software supplied with the camera. Once stored in the computer, the image can be manipulated and processed much like the image from a scanner or related input devices.

10. Bar Code Reader

Bar Code Reader

Bar Code Reader, also called as bar code scanner is a input device that uses laser beams to read bar codes on products such as groceries, books and packages.

Light Pen

11. Light Pen

Light pen is used as pointing device, which is very sensitive to light. Light pen uses a photoelectric (light-sensitive) cell to communicate the screen position to the computer. When the light pen tip is places against the screen, it is capable of sensing its position on the Cathode Ray Tube (CRT). As the tip of the pen is moved over the surface of the screen, its light sensitive elements detects the light emitted from the screen. We can select the desired option of the menu by touching light pen against desired option. Now days, light pens are used in menu big hotels room for the customer for selecting their choice of menu and other items.

Touch Screen

12. Touch Screen

This is easiest way to enter data using the finger touch. Touch screens enable the user to select an option by pressing a specific part of the screen. Touch screens are commonly used in grocery stores, fast food restaurants, and information centers.

Touch Pad

13. Touch Pad

Many laptop computers use a touchpad in front of the keyboard. We move our finger on the pad to move the cursor on the screen. When we want to click, we can tap pad or use the buttons in front of the pad, which works like mouse buttons.

14. Microphone

Micro Phone

Microphone is used to give voice commands to the computer or we can chat with someone with the microphone in the internet.