Input an Output Devices

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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.

    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.

    On Line Data Entry Devices

    Key

    Board

    Mouse Touch

    Screen

    Light

    Pen

    Track

    Ball

    Joy Stick Voice

    Recognizer

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    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 softwares 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 upand 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 speciallypatterned 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 doesnt 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 Packards 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, thescreen 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 users 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 ATMs, Mobile phones.

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    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.

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    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

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    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 onlinesystem 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 helpto 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.

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    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.

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    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 canhandle 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 becontrolled 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.

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    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 andmodern 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.

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    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 wandis the simplest barcode reader. It contains no moving parts and is known for its durability and low

    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.

    b. A slot scannerremains 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.

    c. A CCD scannerhas 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.

    d. 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.

    e. 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 holders identity,

    address, insurance data, relatives 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.

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    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 asinvoices 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 storesup 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

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    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, writtendocuments 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

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    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 LCD Plasma

    1. Having high dynamic range

    of colors, wide gamut and

    low black level.

    1. Very compact and light

    weighted.

    1. Compact and light weighted.

    2. It can display natively in

    almost any resolution and

    refresh rate.

    2. Low power consumption. 2. High contrast ratios,

    excellent color, wide gamut

    and low black level.

    3. It has low response time

    generally in Sub-

    milliseconds.

    3. No geometric distortion. 3. High speed response time.

    4. It has zero color, saturation,

    contrast or brightness

    distortion as well as

    excellent viewing angle.

    4. Little or no flicker depending on

    backlight technology.

    4. Near zero color, saturation,

    contrast or brightness

    distortion as well as

    excellent viewing angle.

    5. Usually much cheaper than

    LCD and Plasma.

    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)).

    Disadvantages:

    1. Large size and weight,

    especially for bigger screens

    (a 20-inch unit weighs about

    20 to 30 Kg).

    1. Limited viewing angle, causing

    color, saturation, contrast and

    brightness to vary, even within the

    intended viewing angle, by

    variations in posture.

    1. Large pixel pitch, meaning either

    low resolution or a large screen.

    2. High power consumption. 2. Uneven backlighting in some

    monitors, causing brightness

    distortion, especially toward the

    edges.

    2. Noticeable flicker when viewed at

    close range.

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    3. Geometric distortion caused

    by variable beam travel

    distances.

    3. Slow response times, which

    cause smearing and ghosting

    artifacts. Modern LCDs have

    response times of 8 mini seconds or

    less.

    3. Only has one native resolution.

    Displaying other resolutions

    requires a video scalar, which

    degrades image quality at lower

    resolutions.

    4. Older CRTs are prone to

    screen burn-out.

    4. Only one native resolution.

    Displaying resolutions either

    requires a video scalar, loweringperceptual quality, or display at 1:1

    pixel mapping, in which images will

    be physically too large or won't fill

    the whole screen.

    4. Only has one native resolution.

    Displaying other resolutions

    requires a video scalar, whichdegrades image quality at lower

    resolutions.

    5. Produces noticeable flicker

    at low refresh rates.

    5. Fixed bit depth, many cheaper

    LCDs are incapable of producing

    true color.

    5. Fixed bit depth, many cheaper

    Plasma are incapable of

    producing true color.

    6. In a constant on situation,

    thermalization may occur, which is

    when only part of the screen has

    overheated and therefore looks

    discolored compared to the rest of

    the screen.

    6. Dead pixels are possible during

    manufacturing.

    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.

    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.

    Printers

    Impact Type Non-Impact Type

    Character or Serial

    Printer

    Line Printer

    Dot Matrix

    Printer

    Daisy Wheel

    Printer

    Drum TypeChain Type

    Chain Type

    Thermal

    Printer

    Ink Jet

    Printer

    Laser

    Printer

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    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 butin 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/microcomputers.

    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

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    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 eitherDrum type orFlat 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.

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    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 high-

    quality 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

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    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 above6. 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 Mousec) 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

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    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