Course Name: Computer Application LECTURE Course Name: Computer Application Topic: Output Devices

Output Devices An output device is any piece of computer hardware used to communicate the results of data processing into human-readable form. Following are important output devices: Monitors Printer Plotter Speaker and Headphones Speech synthesisers

Monitors Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels. There are two kinds of viewing screen used for monitors. Cathode-Ray Tube (CRT) Flat-Panel Display Monitor

Cathode-Ray Tube (CRT) Monitor The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity, or resolution. It takes more than one illuminated pixel to form whole character, such as the letter ‘e’ in the word help. A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically. There are some disadvantages of CRT Large in Size High power consumption

Flat-Panel Display Monitor These take up a lot less room on a desk and use less energy than the traditional, more bulky monitors. The visual quality of these monitors are very high. The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, videogames, monitors, laptop computer, graphics display. The flat-panel display is divided into two categories Emissive Displays - The emissive displays are devices that convert electrical energy into light. Example are plasma panel and LED(Light-Emitting Diodes). Non-Emissive Displays - The Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. Example is LCD(Liquid-Crystal Device)

Liquid Crystal Display (LCD) Less space Lighter Low power consumption Expensive Limited viewing angle Found on watches, calculators, digital cameras and notebook computers

Light Emitting Diode (LED) Less space Lighter Very expensive Provide higher contrast and better viewing angles than LCD monitor

What is display resolution Describes the sharpness and clarity of image The higher the resolution, the sharper the image and the more that can display on the monitor What is dot pitch Measure of the distance between pixels Sometimes called pixel pitch Smaller the distance between the pixels, the sharper the image What is refresh rate Speed at which monitor redraws images on the screen

What is a video card Converts digital output from computer into analog video signal Controls how display device produces picture Also called graphics card or video adapter How does video travel from the processor to a CRT monitor Processor sends digital data to video card Video card converts digital data to analog signal Analog signal sent via cable to CRT monitor CRT separates signal into red, green, and blue signals Electron guns fire color signals to front of CRT Image displays

Printers What is the resolution of a printer Printer is an output device, which is used to print information on paper. Output device that produces text and graphics on paper Result is hard copy, or printout What is the resolution of a printer Sharpness and clarity of characters Measured by number of dots per inch (dpi) There are two types of printers Impact Printers Non-Impact Printers

Impact Printers Ideal for printing multipart forms The impact printers print the characters by striking them on the ribbon which is then pressed on the paper Ideal for printing multipart forms Can withstand dusty environments, vibrations, and extreme temperatures Characteristics of Impact Printers are the following Very low consumable costs Very noisy Useful for bulk printing due to low cost There is physical contact with the paper to produce an image These printers are of two types Character printers Line printers

Character Printers Character printers are the printers which print one character at a time. These are further divided into two types Dot Matrix Printer(DMP) Daisy Wheel Dot Matrix Printer Dot matrix printers work by firing a row of pins, through an ink ribbon, onto the paper. The more pins the print head has the higher the quality of the print, most dot matrix printers have 24 pins. Most use continuous-form paper Dot matrix printers are used for high volume / low quality printing, e.g. printing company pay slips Advantages Inexpensive Widely Used Other language characters can be printed Disadvantages Slow Speed Poor Quality dot matrix printers can generate a lot of noise and do not produce a very high quality of print, especially when printing graphics.

Daisy Wheel Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower name) that is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices which require a few letters to be sent here and there with very nice quality. Advantages More reliable than DMP Better quality The fonts of character can be easily changed Disadvantages Slower than DMP Noisy More expensive than DMP

Line Printers Advantages Disadvantages Line printers are the printers which print one line at a time. These are of further two types Drum Printer Chain Printer This printer is like a drum in shape so it is called drum printer. The surface of drum is divided into number of tracks. Total tracks are equal to size of paper i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on track. The different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute. Advantages Very high speed Disadvantages Very expensive Characters’ fonts cannot be changed

Character fonts can easily be changed. Chain Printer In this printer, chain of character sets are used so it is called Chain Printer. A standard character set may have 48, 64, or 96 characters. Advantages Character fonts can easily be changed. Different languages can be used with the same printer. Disadvantages Noisy

Non-impact Printers Characteristics of Non-impact Printers Forms characters and graphics on piece of paper without actually striking paper Non-impact printers print the characters without using ribbon. These printers print a complete page at a time so they are also called as Page Printers. These printers are of two types Laser Printers Inkjet Printers Characteristics of Non-impact Printers Faster than impact printers. They are not noisy. High quality. Support many fonts and different character size.

Laser Printers Disadvantages Advantages They use laser lights to produce the dots needed to form the characters to be printed on a page. Laser printers produce high print quality at high speed. They are called "laser printers" due to the fact that they contain a small laser within them. Advantages Very high speed Very high quality output Give good graphics quality Support many fonts and different character size Disadvantages Expensive.

Expensive as cost per page is high Slow as compared to laser printer Inkjet Printers Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features. Inkjet printers are ideal for low volume printing, where high quality print is required and speed is not an issue, such as printing letters in a small office or in the home. They make less noise because no hammering is done and these have many styles of printing modes available. Colour printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also. Advantages High quality printing More reliable Disadvantages Expensive as cost per page is high Slow as compared to laser printer

INPUT & OUTPUT BOTH DEVICES A modem can be used for downloading information from web sites and receiving emails. It can also be used for uploading and sending emails. A touch screen can display a menu system (output device), and accept input when people touch the menus displayed on the screen.

Speakers and Headphones Plotters A plotter is an output device similar to a printer, but normally allows you to print larger images. Sophisticated printer used to produce high-quality drawings Large-format printer similar to plotter and is used to print quality color prints Speakers and Headphones Most computers are sold with the capability to add a pair of speakers to your system unit. In fact, in some cases, the computer screen may have speakers built directly into the unit Most computers allow you to plug headphones into one of the computer sockets. This is useful as the sound will then not annoy others in the room. Enhances the value of educational and presentation products.

Speech synthesisers A recent development is the ability not only to display text on a monitor but also to read the text to you You could receive a text email from a colleague and the system could read that email to you This is of enormous benefit to the visually impaired when using a computer On the flip side, it is now possible to use a microphone to talk to the computer and for the computer to directly convert the spoken word into text, which will be displayed within a word-processor Whilst these systems are far from fool proof they are getting better as more advanced software is being made available. Gives you the ability to not only to display text on a monitor but also to read the text to you

Projectors These are projection devices which can be attached to your computer and are useful for displaying presentations to a group of people. They are best used in combination with presentation programs, such as Microsoft PowerPoint. They are used within education and are also very popular for sales presentations.