Input an Output Devices

October 7, 2017 | Author: Krishna Chaitanya Mogallapalli | Category: Printer (Computing), Barcode, Image Scanner, Computer Monitor, Display Resolution
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Chapter2 Input and Output Devices The Scope of this chapter is below: • Different types of input and output devices available and how to use them. • Where to use the right kind of input and output device. • Add-ons required for the input Devices. An I/O device is the short name used for Input/Output devices generally. Input devices used to send the data or information from the outside world to the computer, where as the output devices are used to display the data or information contained in the computer to the outside world either from the computer or from any other device or computer. A. Input Devices: The devices used for sending the data or information from the outside world to

the computers is categorized as the input devices, these can be further classified into On-line Entry Devices and Direct Data Entry Devices. 1. Online Entry Devices: These devices use techniques for data entry that avoid capturing the data on the paper i.e. that allow the data capturing directly into the computer. On Line Data Entry Devices

Key Board


Touch Screen

Light Pen

Track Ball

Joy Stick

Voice Recognizer

1.1. Key Board: This is the most popular input and control device for data entry and to issue

commands. • The keyboard is just like a type writer machine except that it contains only keypads. Keypads contain number of keys meant for different functions like normal alphanumeric keys and special symbol keys etc. • There are many different keyboard layouts and sizes with the most common for Latin based languages based on QWERTY layout. Keyboard is normally divided into some areas as per various types of keypads on the keyboard. Function keypad contains the function keys which are programmable for specific functions. Example, “F1” to search for help, “F12” to trigger the ‘save as’ option, “F7” to trigger the ‘spelling and grammar check’. Also called as soft keys as when tapped they execute software. Number Keypad contains number keys for the rapid numeric data entry; this also contains Num lock for on and off the number pad. Arrow keypad contains arrow keys or cursor control keys, these allow the user to move the cursor position up and down, left and right.

Multimedia keypad contains the keys for controlling the multimedia functions like increase volume, pause/play the movies etc. Other important keys are – Caps lock, Shift key, Scroll lock, page up, page down, Esc, Spacebar, Home, End and Print screen. 1.2. Mouse: In most of the computer today the keyboard is supported with one another type of

input device called mouse, this makes the cursor movement very fast on the screen. • Cursor is a screen element which indicates the location of data entry on screen. With a keyboard the movement of the cursor can be left, right, up and down, where as using mouse the cursor can be placed any where on the screen just by a click on the mouse buttons. • Mouse can be used with GUI (Graphical User Interface) based software’s like Windows or LINUX. • Mouse can be of one, two or three button types. Each button has a specific action, like left button is used to place the cursor or selecting the function; right button will display routine functionalities like cut, copy, paste etc and middle button to scroll the screens up and down. • Based on the technology used mouse can be mechanical mouse, Optomechanical mouse and Optical Mouse. Mechanical Mouse- small round ball(also referred as trackball) projects through the bottom surface rotates as the mouse is moved along a flat surface. The direction of rotation is detected and relayed to the computer by the switches inside the mouse. Optomechanical mouse- is the same as the mechanical mouse except that it uses optical sensors to the motion of the ball. A mouse pad should be used under the mouse to run on. An optical mouse- uses a laser instead of a rotating ball to detect movement across a specially patterned mouse pad. Optical mouse do not have any mechanical moving parts. The cordless mouse- uses the wireless communication technology (via infrared, radio or Bluetooth) to transmit data to the computer. And like the wireless, it doesn’t use any cord. Mouse connects to PCs thru - RS-232C serial port, PS/2 port or USB port. USB port is the latest port, and other advantage is it can be easily connected to computer from front or back or either sides of computer case. 1.3. Touch Screen: The concept of touch screen is Hewlett Packard’s innovation in 1984. The

computer screen is made sensitive to the human fingers. By pressing the finger against the function displayed on the screen infrared beam is broken and the function is activated. •

Two popular technologies exist for touch screens In one technology type, the screen is sensitive to touch and exact position of touch is detected. In other, screen is lined with light emitting devices (LEDs) on its vertical sides; photo-detectors are placed on the horizontal sides. When the user’s finger approaches the screen, the light beam is broken and is detected by the photo detectors. • Touch screen systems are mainly used to provide the user friendly navigation, input and output systems. Examples: - The touch screen technology is very popularly seen in ATM’s, Mobile phones.

1.4. Light Pen: Light pen is mainly used with display device. This device looks like normal

pen but the entire thing will be written on a flat screen directly. A light pen has a photo-detector at its tip. This detector can detect changes in brightness of the screen. When the pen is pointed at a particular point on the screen, it records the instant change in brightness that occurs and informs the computer about this. The computer can find out the exact spot with this information. Thus, the computer can identify where the user is pointing on the screen.

• When a light pen is placed near the screen; the computer system can determine its position on the screen because the light pen contains the light sensitive tip. • This pen is mainly used to draw hand free drawings on the screen or to highlight any part that is already displayed on the screen like selecting a menu option. • Also the light pen is useful for drawing graphics in CAD. An engineer, architect or fashion designer can draw directly on the screen using the light pen. • Light Pen can be used only on CRT monitors but not on LCD, LED or OLED monitors.

1.5. Track Ball: Track ball is a pointing device that works like an upside-down mouse.

• The user rests his thumb on the track ball and fingers on the buttons. In order to move the cursor position the track ball is rolled with the thumb. • This technology is popularly used in the notebooks. But the latest notebooks are coming with the touch pad for the cursor movement. 1.6. Joy Stick: It is a screen pointing input device. It is a vertical lever usually placed in a ball socket, which can be fitted in any direction to control cursor movements for computer games and for some professional applications. 1.7. Scanner: It is an input device used for optically scans images, printed text, handwriting, or

an object, and converts it to a digital image. • The common examples found in offices are variations of the desktop (or flatbed) scanner where the document is placed on a glass window for scanning. • Capturing information like this reduces the possibility of errors typically experienced during large data entry. Hand-held scanners are also commonly seen in big stores to scan codes and price information for each of the items (Code Readers). 1.8. Camera: Two types of cameras are used for input on a computer.

• The digital camera is a device that takes digital images and saves them to memory. The user then connects the camera to the computer where images are uploaded and saved. • Web cams are the other type of camera that is known as video capture device that is connected to a computer or computer network, often using a USB port. Web cams are ways for people to take images from the computer and communicate visually with other users on the Internet. 1.9. Voice Recognizer: The “Microphones - Speech Recognition” is a speech Input device. Presently sound capabilities are a standard part of computers; microphones are becoming increasingly important as input devices. Sound is used most often in multimedia, where the presentation can benefit from narration, music, or sound effects. In software, sounds are used to alert the user to a problem or to prompt the user for input.

• For this type of input, we require a microphone and sound card to translate electrical signals from microphone into a digitized form that the computer can store and process. Sound cards can also work vice versa, converting digitized data into sound and send back to speakers. • Microphones are used in many applications such as telephones, tape recorders, hearing aids, motion picture production, live and recorded audio engineering, in radio and television broadcasting and in computers for recording voice, speech recognition, VoIP. • Translating voice to text is a capability known as voice recognition (or speech recognition). With it, one can speak to the computer rather than having to type. The user can also control the computer with oral commands, such as “shut down” or “print status report”. • Voice recognition software takes the smallest individual sounds in a language, called phonemes, and translates them into text or commands. Even though English uses only about 40 phonemes, a sound can have several different meanings (“two” versus “too,” for example) making reliable translation difficult. 1.10. Digitizing Tablet: It is also known as graphics tablet which is a computer input device that

allows hand-draw images and graphics, similar to the way one draws images with a pencil and paper. • These tablets may also be used to capture data or handwritten signatures. It can also be used to trace an image from a piece of paper. • A graphics tablet consists of a flat surface upon which the user may "draw" or trace an image using an attached stylus, a pen-like drawing apparatus. The image generally does not appear on the tablet itself but, rather, is displayed on the computer monitor.

1.11. MIDI Devices: MIDI (Musical Instrument Digital Interface) is a system designed to

transmit information between electronic musical instruments. A MIDI musical keyboard can be

attached to a computer and allow a performer to play music that is captured by the computer system as a sequence of notes with the associated

2. Display Devices: It is a known fact that the one who interacts with computer uses a display device. These display devices consist of a television like viewing screen to display both input and outputs. The two most common types of display devices found today are monitors and terminals. Monitors are the display devices found mostly with Micro computers. Computer terminal (VDT) are mostly found in remote settings with Main computer and interact with main computer using communication lines or networks, example – Air line agents, Railway ticket booking points. There can be several types of terminals as discussed below: 2.1. Dumb Terminal: These are known as limited function terminal i.e. no data processing or programming facilities are available in these terminals. These terminals are used for just entering the data in the system and to view the outputs. These are normally used in the online system for punching the data into computer system for processing purpose, example some data entry operator is provided the dumb terminal just to do the voucher entry. 2.2. Intelligent terminals: These are most expensive terminals than the dumb terminals.

Intelligent terminal are programmable terminal i.e. these terminals contain the inbuilt processing capabilities and storage facilities. •

These terminals can be used to perform many processing functions like arithmetic and logical operations like (Sorting, Summarization etc.), without sending data to mainframe, which help to save time and also act as back up to mainframe. • All the micro computers are intelligent terminals because every micro computer terminal (Key board and VDU) is connected with CPU which can process the data. • In mini computer and mainframe, terminal can be defined according to the user, if a terminal is used only for data entry by the data entry operator, it may be a dumb terminal and if the computer can be used by a programmer or senior executive for some processing purpose then this terminal will be intelligent terminal. 2.3. Smart terminal: Contain a micro processor and some internal storage. They have data editing

capability and can consolidate the data before sending it to CPU. These terminals are non programmable by users.

2.4. Remote Job terminal (RJE): Also termed as Remote Job Entry, the terminals which

communicate with the main CPU from a remote location with the help of some communication devices (direct cable or Telecommunication lines) are called as Remote terminals. • These terminals group the data into blocks for transmission to CPU from a remote site. Some terminals have the capability of receiving back and printing the results of the application program. •

Terminals linked to the computer system by a direct cable are known as hard-wired terminals. However, for remote terminals, communication to the main system can be established via telecommunication lines such as ordinary telephone lines.

2.5. Keyboard printer terminal (teletypewriter): These terminals consist of keyboard for

sending information to the computer and a printer, for providing a copy of the input and for receiving the information from the computer. 3. Features of display devices:

There are various types of display devices available in the market. Here are some of the important features which distinguish one display device with other. 3.1. Screen Resolution: One of the most important features to differentiate the display devices

is clarity or resolution of the images formed on the screen. Most display devices form the images from tiny dots called “pixels” that are arranged in a rectangular pattern. The more dots available to display any image on screen, the sharper the image is. Images on screen are formed with the help of a card called display adaptor card. The type of the display adaptor determines the quality of image on the screen. Display adaptors mainly provide two features, which determine the quality of output. 1. Resolution (Video Controller) 2. Memory Following are the technological improvements over the year in the adaptor technology for resolution and memory capability. 1) MGA – Monochrome Graphics Adaptor, it is a text – only adaptor works only with

Monochrome monitor. 2) CGA – Color Graphics Adaptor works both with text and graphics mode. However, it has

relatively poor display quality in text mode. CGA has a resolution of either 640 x 200 pixels with 16 colors or 320 x 200 pixels with 4 palettes. 3) EGA – Enhanced Graphics Adaptor combines features of CGA & MGA, it supports up to 16

colors at a time. An EGA usually has a high resolution of either 640 x 200 pixels or 640 x 350 pixels. 4) VGA – Video Graphics Adaptor is a high quality graphics adaptor which provides up to 256

colors and also a high resolution. VGA has high resolution of 640 x 480 pixels with 16 colors or 320 x 200 pixels with 256 colors.

5) SVGA – Super Video Graphics Adaptor is an improvement on the VGA. The combinations of

resolution and colors provided by SVGA are – 640 x 480 pixels with 256 colors 1024 x 480 pixels with 16 colors Beside these early versions of Super Video Graphics Adapter(SVGA), variations include Wide SVGA (WSVGA) ,eXtended GA(XGA), Super eXtended GA(SXGA), Wide eXtended GA(WXGA), and UXGA which are commonly used technology ranging from 1024 x 600 pixels to 1600 x 1200 pixels that covers a wide range of computer display standards now-a-days. Digital monitors such as small flat panel LCD monitors come in usually XGA, SXGA and other formats. These monitors usually have resolution rates of either 1024 x 768 or 1280 x 800. While digital computer monitors can handle the enhanced resolution, it is up to the end user to choose the settings. Many people choose a SVGA setting of only 800 x 600 resolutions. Digital TV sets such as HDTV sets have increased screen resolution. Because HDTV sets can handle more lines per screens, their image quality is dramatically increased. 3.2. Text and Graphics: Many display devices made today (except very few those used in

dedicated transaction processing applications) can produce both text and graphics output. Text output is composed entirely of alphabetic characters, digits, and special characters. Graphics output includes such images as drawings, charts, photographs, and maps. •

Display devices that are capable of producing graphics output commonly employ a method called bit mapping. Bit-mapped devices allow each individual pixel on the screen to be controlled by the computer. 3.3. CRT Vs Flat-Panel: The display devices, which are like picture tube TVs are of CRT

(Cathode Ray Tube) type. But these days flat panel display devices are becoming more popular. Laptops are coming with flat panel display, even micro computers monitors started using the Flat-panel display devices which are light weight and compact. • Flat panel display devices are costly compared to CRT but provides better clarity, resolution with low power consumption. These Flat panel devices use LCD (Liquid crystal display) or gas-plasma technology or LED technology. • To form images LCD devices use crystalline materials sandwiched between two panes of glasses. When voltage is supplied the crystals line up. This prevents light from passing through certain areas and produces the display. • Gas-plasma uses gas trapped between glass to form images. They provide better resolution than LCD but are more expensive. Video Controller: The quality of the images that a monitor can display is defined by the video controller. The video controller is an intermediary device between the CPU and the monitor. • It contains the video-dedicated memory and other circuitry necessary to send information to the monitor for display on the screen.

It consists of a circuit board, (“video card” ) which is attached to the computer’s motherboard. The processing power of the video controller determines the refresh rate, the resolution, and the number of colors that can be displayed. • Video controllers have increased dramatically in power and importance. There is a microprocessor on the video controller, and the speed of the chip limits the speed at which the monitor can be refreshed. Most video controllers today also include at least 128 MB of video RAM, or VRAM. (This is in addition to the RAM that is connected to the CPU.)

• VRAM is “dual-ported,” meaning that it can send a screenful of data to the monitor while at the same time receiving next screenful of data from the CPU. It’s faster and more expensive than DRAM (Dynamic RAM). Users with larger monitors or with heavy graphics needs usually will want even more than 128 MB that can go upto 4 GB of VRAM.

4. Direct Data Entry (DDE) Devices: These are the devices, which enter data directly into the computers through machine readable source documents. DDE does not require any manual transcription of data from original paper documents. These devices can scan source documents magnetically or optically to capture data fro direct entry into the computer. Some of the popular Direct Data entry devices are Scanners: These input devices are mainly used for entering large amount of data or transaction which, are in printed or image form. These devices normally operate on magnetic or optical principle i.e. these devices read the input from the source documents with the help of some magnetic or optical device and then convert these to computer readable format. Two types of Scanners, they are Magnetic and Optical. 4.1. MICR (Magnetic Ink Character Reader): This input device mainly used in the banking industry for reading character coated with special type of magnetic ink on the bottom of the cheque or draft. The information encoded on the bottom of the cheque and draft contains the number, bank identification number and branch number etc. When a cheque is submitted to bank by a customer, it is sent to the data processing center of that bank. This cheque is then processed with thousands of other similar cheques through a Magnetic Ink Character Reader unit. How MICR read the data; When cheque passes through the MICR unit it contain a strong magnetic field which demagnetized the character which contains some binary code, this binary code is matched with original one, which is saved in MICR machine for verification purpose. If code does not matched or MICR unable to read the character then cheque is rejected otherwise the MICR will process the cheque. After processing, cheques are sorted according to the bank number etc.

Advantages 1. Automatic processing of cheques except entry of amount. 2. It can read the data with very high accuracy despite the cheque being used roughly i.e. it can read from smeared or stamped cheque with high accuracy. 3. The magnetic characters are both machine and human readable. Disadvantages 1. Only small number of characters are used; 10 digits (0 to 9) and 4 special characters, so not very popular. 2. It is not fully automated technique, as the cheque amount needs to be entered manually. 3. MICR readers and encoders are expensive. 4.2. Optical Character Reader (OCR): These are widely used device for direct data entry. These

• •

• •

devices can read the printed data and can enter this data directly into computer. In general language these are called as optical scanner. Data to be entered into computer, first of all it is scanned through optical device. In scanning the optical device throw the light (optic) on the data and the reflection of light contain the image of the data, which are further converted into electric signals. These electric signals are entered into computer in a computer readable format. Unlike in MICR, in OCR no special ink is required and it can read any type of character and modern scanners are capable reading images also. Thus no input keying is required for direct data entry by using the OCR.

4.3. Optical Marks Reader (OMR): This type of device mainly find application where only

marks recognition is required like e.g. CA exam Application, CPT exam answer sheets, and many more competitive exams. In multiple choice question sheets every applicant is required to mark the answer with the help of some pen or pencil on given sheet. Then all the answer sheets are put under the OMR, which scan the marks and convert them into values to compare with the pre defined values and gives the results. • The optical mark reader when online to the computer systems can read up to 2,000 documents per hour. • OMR can also be used for such applications as order writing, payroll, inventory control, insurance, questionnaires, etc. However, it is to be noted that designing the documents for OMR is rather a tough task. • Earlier, OMR were designed to use dedicated scanners and special pre-printed forms with drop-out colors and registration marks. But today, OMR Software makes OMR possible on a desktop computer by using an Image scanner to process surveys, tests, attendance sheets, checklists, and other plain-paper forms printed on a laser printer. 4.4. Bar Codes Reader: Bar codes are commonly used to identify the merchandise in retail

shops. The code for each product is unique combination of ten or more pairs of vertical bars.

This combination of bar contain the information about that particular product which is normally scanned with the help of hand held bar reader or flatbed scanners and product information is directly fed into computer. • Computer program automatically write the type of product and cost in the invoice. This is very important way of keeping track of products because it automatically maintain inventory also. • Bar codes provide advantages of improved accuracy of data entry, fast data entry which helps in providing better customer service with faster checkout at the point of sale in big departmental showroom etc. and it also provides greater control and reliability of inventory records etc. • We can observe this in almost all the supermarkets, readymade showrooms to bill the items purchased. There are five basic kinds of barcode readers – pen wands, slot scanners, Charge-Couple Device (CCD) scanners, image scanners, and laser scanners: a. A pen wand is the simplest barcode reader. It contains no moving parts and is known for its durability and low

b. c.



cost. A pen wand can present a challenge to the user, because it has to remain in direct contact with the bar code, it must be held at a certain angle, and has to be moved over the bar code at a certain speed. A slot scanner remains stationary and the item with the bar code on it is pulled by hand through the slot. Slot scanners are typically used to scan bar codes on identification cards. A CCD scanner has a better read-range than the pen wand, it is a "gun" type interface and has to be held no more than one inch from the bar code. A disadvantage of the CCD scanner is that it cannot read a bar code that is wider than its input face. An image scanner, also called a camera reader, uses a small video camera to capture an image of the bar code and then uses sophisticated digital image processing techniques to decode the bar code. It can read a bar code from about 3 to 9 inches away and generally costs less than a laser scanner. A laser scanner, either hand-held or stationary, does not have to be close to the bar code in order to do its job. It uses a system of mirrors and lenses to allow the scanner to read the bar code regardless of orientation, and can easily read a bar code up to 24 inches away. To reduce the possibility of errors, a laser scanning may perform up to 500 scans per second. Specialized long-range laser scanners are capable of reading a bar code up to 30 feet away.

4.5. Smart Card System: Smart cards resemble credit cards in size and shape; however, they

contain a microprocessor chip and memory. Smart cards are used most frequently to make electronic purchases and to electronically transfer funds between accounts. However, these are used in many applications. For example, in the health care industry; smart cards could be used to store the holder’s identity, address, insurance data, relative’s details, allergies, and even a brief medical history. If the cardholder was disabled by an accident or illness, the card could be used immediately to assist with treatment. Smart cards could also be used for security applications. For example, a card could contain the digitized fingerprint of the cardholder, which could be compared at a security checkpoint to fingerprints of people who are authorized to enter a secured area.

5. Document Imaging or Image Scanning:

Image Processing captures an electronic image of data so that it can be stored and shared. Imaging systems can capture almost anything, including keystroked or handwritten documents ( such as invoices or tax returns), flowcharts, drawings, and photographs. Many companies that use document imaging are making significant progress toward paperless offices. There are five distinct steps to document imaging: Step1: Data capture. The most common means of converting paper documents into electronic images is to scan them. The scanning device converts the text and pictures into digitized electronic code. This scanner can range from a simple hand held device to a high-end, high-speed scanner capable of scanning more than 2,500 pages an hour. Hand held scanners could transform text or graphical images into machine-readable data. Step2: Indexing. Document images must be stored in a manner that facilitates their retrieval. Therefore, important document information, such as purchase order numbers or vendor numbers, is stored in an index. Great care is needed in designing the indexing scheme, as it affects the ease of subsequent retrieval of information. Step 3: Storage. Because images require a large amount of storage space, they are usually stored on an optical disk. One 5.25-inch optical platter can store 1.4 gigabytes, or about 25,000 documents (equivalent to 3 four-drawer filing cabinets) A 12-inch removable optical disk stores up to 60,000 documents, and up to 100 optical disks can be stored in devices called jukeboxes. Step 4: Retrieval. Keying in any information stored in an index can retrieve documents. The index tells the system which optical disk to search and the requested information can be quickly retrieved. Step5: Output. An exact replica of the original document is easily produced on the computer.s monitor or on paper, or is transmitted electronically to another computer. Advantages of Image Processing: It has been estimated that 90% of the work accountants and others do today is done using paper. It is also estimated that the volume of information required by companies doubles every three or four years. As a result we are faced with being buried by paper. One solution is to make better use of document imaging. More companies are moving to

this technology and it is estimated that by 2004 only 30% of our work will be paper-based; 70% will be electronic. The move to document imaging provides the following advantages: (i) Accessibility : Documents can be accessed and reviewed simultaneously by many people, even from remote locations. (ii) Accuracy : Accuracy is much higher because costly and error-prone manual data-entry processes are eliminated. (iii) Availability : There are no more lost or misfiled documents. (iv) Capacity: Vast amounts of data can be stored in very little space, which significantly reduces storage and office space. (v) Cost : When large volumes of data are stored and processed, the cost per document is quite inexpensive. As a result, the costs to input, file, retrieve, and refile documents are reduced significantly. (vi) Customer satisfaction : When waiting time is significantly reduced (due to lost or misfiled documents, queue time, etc.), customers can get the information almost immediately. (vii) Security : Various levels of passwords (network, data base, files, etc.) and clearances can be assigned to restrict document access. (viii) Speed : Data can be retrieved at fantastic speeds. Stored documents can be indexed using any number of identifying labels, attributes, or keywords. (ix) Versatility : Handwritten or types text can be added to an image, as can voice messages. Documents can be added to word processing files; the data can be included in a spreadsheet or data base. B. Output Devices: Computer Output devices are pieces of computer hardware that allow a computer system to communicate information to a user or another system. This information can be in any form, and includes sound, images, written documents etc. Output devices can usually only be used to send data from the computer; items called input devices allow users and other systems to send data to the computer. Some of the most common output devices allow computers to present information visually. The visual display unit called a monitor that can be found connected to almost every personal computer is the best example of this. Text, pictures, and other images are displayed on the monitor, allowing users to interact with computer programs and receive data. Video projectors are another type of output device. They function in a way similar to monitors, but display images over a much larger area. Computer printers are another type of output device that can be easily found. Printers allow the computer to produce documents, pictures, and images on paper through the use of inks and other dyes. Audio output devices are also common. Computer speakers are the primary source of this form of output. They allow the computer to emit sounds that include music, audio tracks to digitized television shows, and even the voices of other users. Headphones also do the same thing, but are placed closer to the ears so that the sounds can not be heard by others.

The devices used to display the data or information from the computer to the outside world are categorized as output devices. These devices are used to provide output of data and information from a computer. 1) Monitors 2) Printed Output 3) COM (Computer Output on Microfilm) 4) Audio System(Speaker) 5) Graphical

1) Monitors: A monitor is also called as video display terminal (VDT). Computer monitors

come in a variety of screen sizes. Two types of computer monitors – CRT and Flat pannel . • Resolution – This will indicate the quality of the picture displayed on the monitor, higher the resolution the higher the quality. More dots per inch will make higher resolution, therefore 1024 x 768 resolutions will be sharper than 800x600 resoltions.

Refresh rate: This indicates how many times per second the screen is repainted. Monitors have different refresh ratios, lower resolution refresh rate will be higher. If refresh rate is 85Hz the screen will be repainted or refrshed 85 times per second.

Advantages and Limitations of CRT, LCD and Plasma display devices CRT 1. Having high dynamic range of colors, wide gamut and low black level. 2. It can display natively in almost any resolution and refresh rate. 3. It has low response time generally in Submilliseconds. 4. It has zero color, saturation, contrast or brightness distortion as well as excellent viewing angle. 5. Usually much cheaper than LCD and Plasma.

1. Very weighted.

LCD compact



2. Low power consumption.

3. No geometric distortion.

4. Little or no flicker depending on backlight technology.

Plasma 1. Compact and light weighted.

2. High contrast ratios, excellent color, wide gamut and low black level. 3. High speed response time.

4. Near zero color, saturation, contrast or brightness distortion as well as excellent viewing angle. 5. No geometric distortion. 6. Highly Scalable, with Less weight gain per increase in size (from less than 30 inches (760 mm) wide to the world's largest at 150 inches (3,800 mm)).


1. Large

size and weight, especially for bigger screens (a 20-inch unit weighs about 20 to 30 Kg).

2. High power consumption.

1. Limited viewing angle, causing 1. Large pixel pitch, meaning either color, saturation, contrast and low resolution or a large screen. brightness to vary, even within the intended viewing angle, by variations in posture. 2. Uneven backlighting in some 2. Noticeable flicker when viewed at monitors, causing brightness close range. distortion, especially toward the edges.

3. Geometric distortion caused

3. Slow response times, which 3. Only has one native resolution.

by variable beam travel distances.

cause smearing and ghosting Displaying other resolutions artifacts. Modern LCDs have requires a video scalar, which response times of 8 mini seconds or degrades image quality at lower less. resolutions. 4. Only one native resolution. 4. Only has one native resolution. Displaying other resolutions Displaying resolutions either requires a video scalar, which requires a video scalar, lowering degrades image quality at lower perceptual quality, or display at 1:1 resolutions. pixel mapping, in which images will be physically too large or won't fill the whole screen. 5. Fixed bit depth, many cheaper 5. Fixed bit depth, many cheaper LCDs are incapable of producing Plasma are incapable of true color. producing true color. 6. In a constant on situation, 6. Dead pixels are possible during thermalization may occur, which is manufacturing. when only part of the screen has overheated and therefore looks discolored compared to the rest of the screen.

4. Older CRTs are prone to screen burn-out.

5. Produces noticeable flicker at low refresh rates.

2) Printed Output:

Printed output is most common or popular form of output of computer. This form of output can be obtained by using an output device known as printer. Printer is an output device which gives hard copy or printed output of data on paper. Types of Printers: There are two types of printer – Impact printers and Non-Impact printers. Printers

Impact Type

Character or Serial Printer

Dot Matrix Printer

Daisy Wheel Printer

Drum Type

Non-Impact Type

Line Printer

Thermal Printer

Ink Jet Printer

Laser Printer

Chain Type Chain Type

A. Impact Printers: These printers print with hammering or striking the head on paper through a ribbon. These printers will create some sort of noise while printing on paper just like striking some object on hard surface.

Character Printers: These are the printers, which print the data character by character. There are two types of character printers as discussed below. a. Dot Matrix Printer: These printers print each and every character in the form of

matrix with the help of dots. Dot Matrix printer contain a head, which, contains the wire pins arranged vertically 9 in nos. or 24 in nos. etc. 9 pins printer prints one character in the 9x9 form of matrix and 24 pins printer print the same character with higher nos. of dots in the matrix form. 24 pins printer print better quality output as more the nos. of dots per character will be used to produce printed output. In Dot Matrix Printer output is printed by striking pins head on the paper with a ribbon and ribbon puts the impression on the paper similar to a simple typewriter machine. Characters are printed serially in a line. The printing of character can be unidirectional or bidirectional depending upon the printer. Dot Matrix printers have a range of print speeds, print quality and features. Speed of Dot Matrix printer is measured in terms of CPS (Characters per second) normally it prints 200 characters per second. b. Daisy Wheel Printer: This impact printer is just like an electric typewriter. In this

printer there is a circular plastic or metal wheel that looks like a daisy flower with a round center around which the daisy’s petals grow. The petals in this case are flexible arms with character engraved on them at the end. The wheel rotates and the printing is carried out when the wheel is positioned to the correct character and the print hammer (flexible arm) strikes to produce the output. A daisy wheel can print only the limited types of fonts as it can print the type of character which is already engraved on the wheel arm. This printer can produce the good quality printing just like electronic type writer. But, due to slow speed and limitation in printing the different character styles, it is not popularly used in commercial applications. Line Printer: Line printers print many characters at a time. This type of printer is used when the large volume of output is to be printed and print quality is not as important as the speed. These printers can print from 300 LPM (Line per Minute) to 3000 LPM. Mainly there are two types of printers as discussed below. c. Drum Printer: The drum printer uses a metal drum for printing purpose. This drum

revolves at a high speed, which print the data by striking on paper using hammers through a ribbon. In one rotation of drum one line is printed. Therefore the speed of Drum is Rotation per Minute (RPM) provide speed in line per minute. d. Chain Type: In this type of printer a continuous length of chain is used. This chain is

composed of 5 sections of 48 characters per section. The 48 character are a composite of numeric, alphabetic and special characters. The chain rotates at a high speed over a continuous length paper and in-front of the paper are an ink ribbon and below the paper are a set of 132 magnetic hammer. The chain revolves horizontally and passes all print positions. As the character to be printed comes to print position the hammer behind the paper gets activated, pressing paper against the

inked ribbon, which in turn presses against the appropriate characters on the chain, thereby printing the character on paper. B. Non-Impact Printer: Non-Impact printer produces output without striking on the paper.

These printers are quieter than the impact printers. Following are the popular non-impact printers: a. Thermal Printer: These printers are slow speed serial (character type) Non-Impact printer. These printers work on the principle of a Dot matrix printer and print the output on a heat sensitive paper. The printer contains a print head which prints the character with the help of dots in the form of matrix. In this printer the print head contains the pins, which will be heated and move across the paper and wherever these pins head touch the heat sensitive paper, the color of the paper changes to black or brown. These printers are normally used in medical equipments. The most common use of thermal printer in Fax Machine. The quality of output is not a better quality and hence these are not popular for commercial purposes. b. Ink Jet Printer: These printers also work on the principle of Dot Matrix printer but

in these printers the head contain the ink nozzle in place of wire pins as it contain in a simple dot matrix printer. The droplets (Nozzles) of inks are then guide to a proper position on the paper by some electronic system and ink passes on the paper and a character is formed. The print quality with these printers is much better than the wire pins dot matrix printer. Nos. of dots for one character in these printers is approx 500 or more as compared to 63 or more in dot matrix printer. Ink jet printer can print wide variety of output in different kinds of fonts. These printers are capable of printing graphic output as well as color output also. These printers are normally used for personal applications or office applications connected to a personal/micro computers. c. Laser Printer: This is the most popular type of Non-Impact printer. Laser printer is

highest quality printer compared with all others. Data which is to be printed is transferred from CPU to printer in the form of electrical signals. In printer these signals are converted with beam of laser light into a high intensity invisible image of data on a selenium drum. When paper passes over this drum, this image is transferred on paper and paper get charged at places where the image is transferred. This charged image of data on paper attracts the particles of toner (Dry Ink) when the paper is passes over the toner and they are permanently fixed using heat. Laser printer produces a very high quality output. This printer can print any type and style of fonts, graphic images etc. This printer is mainly used in business correspondence and for preparation of high quality presentation. This is also compatible to take color printouts. These can print 4 to 17 pages per minute with the resolution of 600 dpi to 1200 dpi. 3) COM (Computer Output Microfilm/Microfiche): This is an output technique that records output from a computer as a microscopic image on a roll or sheet of photographic film. Image stored on a COM are same as the images printed on a paper. However the images stored on COM can be reduced by 48 times or smaller than the images

printed on a paper. Microfilm comes in the sizes of 16 mm, 36 mm and 100 mm as the normal photographic roll comes. These are very effective type of media to produce the output. These are also used where the historical record are to be maintained for so many years, as this type of output takes smaller space for keeping large amount of printed records than the paper printed records and these are lesser prone to destruction than the paper records. To record data on a microfilm from a computer a special device known as microfilm recorder is required and in the same way for reading also microfilm reader is required. Cost of recording of data on microfilm is much lesser than the printed data. Even the particular data processing is also possible with in a second from millions of stored character on microfilm with the help of specialized software. Micro film can be of two types in a continuous roll and sheet form. Sheet form film is known as Micro Fiche. 4) Voice Output Devices: These days various computer applications uses the voice output, which is generated by a voice output device that is attached to the computer. Voice output contains the spoken words that are conveyed to user from the computer. Voice output is generated by a technique called the voice synthesizer, which can transform words stored in the main memory into human speech. The words which are converted into sound are first analyzed by a program. The speech is then projected over speakers attached to the computer. Voice output is primarily used in the automatic telephonic enquiries system like by telecom companies and in other types of computerized enquiries example, Railway enquiries, Customer care for mobiles etc. It is also used by banking industry for answering queries from clients regarding bank balances etc. 5) Graphic Output (Graph Plotter): These are the devices used for creating maps, charts, drawings etc on a big size paper sheet. They are normally used when the hard copy output of drawings of good quality and bigger sizes are required. The most popular type of graphics output device is plotter. (Plotter is a similar to a printer but is used only for printing graphical output although the plotter can print alphabetical and numeric letter but these are normally printer for drawings output only). Like printer plotter are also getting faster, less expensive and smarter. The plotter is normally supplied with the CAD/CAM system. The plotter is almost an essential component of CAD system. Plotters normally print with the help of a Pen and it is known as Pen Plotter. Pen Plotter: Pen plotter plot the images on a sheet of a paper by the movements of one or more pens over the surface of paper or by the movement of paper under the tip of a pen. Pen plotter may be either Drum type or Flat Bed type. In drum type of plotter the movement of the sheet takes place under the tip of one or more horizontally moving pens for printing the required image on the paper.

Whereas, in flat bed type of plotter the paper sheet remain fixed, the movement of pens takes place horizontally and vertically to print the required image. If more than one pen is used in the plotter then normally drawings with different colors are possible.

Case Study 1 Automated Scoring of General Assessment Test for Students Introduction In response to education reform In India and accountability requirements, most recently, the Right to Education Act, national agencies, states, and large districts across the country has implemented far-reaching systems that reform educational standards and include large-scale assessments to monitor student achievement of those standards. Basic reform strategies emphasize the need for high academic standards describing what all students should know and be able to do and highquality assessments aligned with those standards. States have developed and implemented assessment programs that correspond to curriculum standards and assess students in designated grade levels and subjects. Challenges The authorities has combined both traditional and innovative measures in the design of large scale assessment programs, most of which include multiple-choice, short answer, open response questions, and writing tasks for elementary, middle, high school, and college students. The teachers and local educators are usually involved in the processes of test development, standard setting, scoring, and interpretation of results. The objective of this case study is to address the challenges faced by the teacher in scoring of the assessment test papers that are returned after test administration. The key challenges faced in the scoring process: – To process vast number of answer sheets. – To provide results in timely manner to meet Department of Education (DOE) deadlines. – To assure 99.9% accuracy of all student results. – To provide highly automated processing with minimum human intervention. – To provide scalable solution to meet peak processing. – To get cost effective solution. Kind of document to be processed Once the test development is completed, the end result is a student test booklet containing various content areas like Computer, Math, Science, etc. Each content area contains multiple test questions. The question could be in form of multiple-choice, short-answer, open-response, or writing. The first page of the booklet and the multiple choice questions has “bubble” areas to fill in the answers. The “bubble” area is a set of blank ovals or boxes that correspond to each question, usually on separate answer sheets of paper or underneath the question. Students use 2 HB pencils to mark their answers, or other information by darkening ovals areas. The student booklet also contains a bar code describing the serial number of the booklet. The serial number binds the student to the booklet. Each sheet of the booklet contains a page number and it is related to the configuration of bubble areas on each page. Solution The customer has implemented automated scoring solution based on Forms Processing application to recognize machine printer character using Optical Character Recognition (OCR), penciled bubbles using Optical Mark Recognition (OMR), handwriting using Intelligent Character

Recognition (ICR) & Barcode technologies off the student test booklet. Students’ booklets are cut into sheets and scanned by high speed scanning systems that use Kodak 840 scanners to create JPEG image files. These image files are then processed by Forms Recognition Processor that is calibrated to recognize various booklets types and the contents of each booklet type including bubble, bar-coded, and machine printed areas. The following diagram depicts the process. The application processes in the following way: ICR for hand printed characters OMR for penciled mark bubbles OCR for machine printed characters Barcode. MULTIPLE CHOICE QUESTIONS: 1. The standard keyboard has ___________ keys. a) 95 b) 101 c) 111 d) None of the above 2. An input device which is used to draw the graphics for engineer, architect or a fashion designer is ________. a) Touch screen b) Light Pen c) Joystick d) Track Ball 3. The terminal that has built in processing capability and is user-programmable also is known as: a) Dumb terminal b) Intelligent terminal c) Smart terminal d) None of the above 4. Display devices that are capable of producing graphics output commonly employ a method called ___________. a) Bit mapping b) Byte mapping c) Word mapping d) None of the above 5. LCD and gas-plasma displays are which kind of display devices? a) CRT Based b) Flat-Panel Based c) Both A and B d) None of the above 6. Which of the technology has the potential of reading handwritten documents straightway? a) OMR b) OCR c) Both A and B d) None of the above 7. A high speed scanner is capable of scanning more than ________ pages an hour. a) 1000 b) 2000 c) 3500 d) 2500 8. Printing is done by spraying ionized ink at a sheet of paper __________. a) By Dot-matrix printer b) By Laser printer c) By Ink-jet printer d) None of the above 9. A 16 MM or 35 MM roll of film contains how many pages of information? a) 1000 to 3000 pages b) 2000 to 4000 pages c) 2000 to 5000 pages d) None of the above 10. The card which translates digital sounds into electric current is known as ________. a) Sound Card b) Smart Card c) Credit Card d) None of the above 11. The mouse which uses wireless technology to operate the computer is known as______. a) Serial Mouse b) USB Mouse c) Cordless mouse d) None of the above 12. The resolution of SVGA is _______________. a) 640 x 480 pixels b) 640 x 840 pixels c) 1024 x 600 pixels d) None of the above

13. How many types of Bar code reader is available for application uses ? a) 3 b) 5 c) 4 d) 6 14. SOHO is the name of which kind of printer. a) Thermal printer b) Line printer c) Ink-Jet printer d) Multi-functional printer

1. b 2. b 3. b 4. a 5. b 6. b 7. d 8. c 9. c 10. a 11. c 12. a 13. b 14. d

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