Computer Studies Notes by SAMEE ARIF
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Transcript of Computer Studies Notes by SAMEE ARIF
Hardware
Input and Output devices
Input: Any data or instructions entered into the memory of the computer. Input is often send to computer by Input devices.
Input Devices: Hardware devices that allows a user to enter data and instruction into a computer e.g. Keyboard, Mouse, Joystick etc.
Input Devices
Manual Input Devices:
They are used by the people to capture data
Most common devices:
Keyboards
Keyboard:
Most commonly used Manual input devices
It is a set of buttons. Each button has a symbol assigned.
Type-writer like input device which allows the user to input Text, Numbers and Instruction into the computer
Type of keys: Numeric Keypad, Navigation Keys and Function keys
Used to input data into applications
Also used to enter command in the computer
Types of keyboard:
QWERTY keyboard
Standard keyboard is called a QWERTY keyboard because of the arrangement of the letters on the top row keys
It key arrangement is similar to that of a typewriter.
Used to input data into applications
ADVANTAGES AND DISADVANTAGES ARE IN THE TABLE!
Numeric Keyboard
Introduction:
Small keyboard that has numbers
Keys found on the right hand side if the computer
Uses:
Used to enter numbers 0 9 and arithmetic operators (+ and etc.)
Used to input put Personal identification numbers (PINs) in ATM
Used in Lockers and safes
Used in some mobiles
Used in Telephones
Chip and PIN devices have numeric keypad
Advantages:
Easy to input numbers
Faster than QWERTY Keyboards for entering numbers only
Small size so they are easy to fit on a mobile
Disadvantages:
Difficult to enter text and other symbols
Can be difficult to use due to small keys
Typing a text message on a phone with numeric keypad is difficult
Concept Keyboard
Introduction:
Triangle grid of keys
Each key has Pictures, symbols or words printed in it
Uses:
Used in Point of sale (POS), Restaurants etc.
Used in Shops
Used in Fast food restaurants
Advantages:
Easy to use (Young children and People with disabilities can also use them)
Enables fast data entry (As there is no need to type whole command)
Are waterproof
It is tamper-proof (function cannot be changed)
Advantages Of Keyboard
Disadvantages Of Keyboard
It is not necessary to buy keyboard as it is usually supplied with a Computer
Lots of practice required in order to type quickly
Entering data with computer is faster than pointing devices
Typing speed is very slow when compared to the speed of computer
Typist can use it with ease
People with wrist and hand problems can find keyboards painful to use
Easy to use (Just press the keys)
Quite large so they take up lot of desk space
It uses a Simple, Familiar, Reliable technology (same as a type writer)
In public locations, they are prone to vandalism
Easy to input symbols and text using keyboard
Pointing Devices:
Piece of hardware that are used to control a pointer on a screen
They are frequently used with Graphical User Interface (GUI)
Most common types of Pointing Devices
Mouse
Touchpad
Tracker ball
Touchscreen
Joystick
Graphic Tablet
Light Pen
NOTE: ALL THE POINTING DEVICES HAS ALMOST SAME USE
Mouse:
Introduction:
It is a Pointing device which allows a user to control the cursor.
User selects items by pressing \ clicking buttons on the mouse
Helps user to point and access items on a computer
Has two buttons and a scroll
Uses:
Often used to control the pointer in GUI
Used for opening, closing programs and flies
Used for moving and deleting flies
Used to select icons or moving around page
Types:
Optical Mouse
Has no moving part (there is no ball underneath it)
Uses a device that emit and sense changes in light to detect the mouses movement
Mechanical Mouse
Has a small ball underneath
When the mouse moves over the desk the ball roll over a flat surface and detect the mouses movement
Advantages
Disadvantages
Faster to select ions and options when compared to a keyboard
People with wrist and hand problems can find it painful to use
Easy to move a pointer on the screen
Must be cleaned regularly
It is small and it takes less space on the desk
It needs a flat surface in order to work properly
Cheap
When gripped too tightly can cause muscle stain
User-Friendly for computer beginners
Difficult to input text with a mouse
IT is easy and convenient to use with a graphical user interface
It is not accurate enough for drawing
Very little finger movement required to reach buttons
IT can be easily vandalized
People with Disabilities have problems in using mouse
Touchpad:
Introduction:
Touch pad is a smooth, pressure and touch sensitive area next to a keyboard on a laptop. Which helps a user to control the cursor on the screen
Has two buttons with same function as mouse buttons
Uses:
User moves a finger over the touchpad in order to control a pointer
Used for opening, closing programs and flies
Used for moving and deleting flies
Used to select icons or moving around page
Advantages
Disadvantages
Usually requires no desk space as it is built into a laptop
Expensive
Easy and fast one finger control
More finger movement needed than any other pointing device
Least prone to dust
Difficult to use when compared to a mouse
Ideal for portable devices
Found in specific devices e.g. laptops
Are built into laptops so there is no need of a separate mouse
People with wrist and hand problems can find it painful to use
It does not require a flat surface
Some operations are difficult to perform when compared to a mouse. Drag and Drop for example.
It wont get clogged with dirt (as can happen in ball mice) therefore performance is never reduced
Small active area makes precise cursor control difficult
Expensive
Tracker Ball:
Introduction:
It is a stationary pointing device with a ball on its top
It is a Pointing device which allows a user to control the cursor by rotating the large ball with your hand
Tracker ball is similar to mice but the ball is on the top of the device instead in the bottom
Its buttons perform same function as the buttons on the mouse
User selects items by pressing / clicking buttons
Uses:
Helps user to point and access items on a computer
Used for opening, closing programs and flies
Used for moving and deleting flies
Used to select icons or moving around page
Used in control room environment
Some arcade gaming machines use tracker ball to control game characters
Advantages
Disadvantages
It does not need a flat surface to move on
Can be difficult to use for applications needing fine control
Not likely to get damaged as a mouse
It is not accurate as a mouse
The pointer can be positioned more accurately on the screen than with a mouse
More expansive than mice
People with wrist / hand problems can use tracker ball
More finger movement is required to move the ball
Use less desk space than mouse because the user does not have to move the entire device
The ball requires more frequent cleaning than mouse
Requires less arm and hand movement than mouse
Rolling a ball is less like pointing
User may need training since they are not standard equipment
Joystick:
Introduction:
It is a pointing device with a vertical lever mounted on a base. The vertical lever can be moved in all directions
It also has buttons with specific use
Uses:
It can also provide input for motorized wheelchair
Popular device for gaming (Like to control the movement of a vehicle or character)
It is also used for controlling fly-by-wire aircrafts
They are also used for ultrasound scanners in hospitals
Advantages
Disadvantages
It allows fast interactions required in most games
It is difficult to select object accurately on screen with joystick
It is easy to move game characters with joystick
Not as easy to control curser when compared to using a mouse
Very simple to get used to
People with hand and wrist issues can find them painful to use
Can be used by disabled people and young children
Difficult to enter text with it
It is easy to use
Difficult to issue commands to computer using a joystick
It is easier to navigate round a screen using a joystick rather than a keyboard
Touchscreen:
Introduction:
It is an input / output touch-sensitive display
Output of touchscreen show us image on the screen, while its input allows you to interact with objects on the screen (e.g. touch the screen to select an option)
It is sensitive to touch of a stylus or a finger
Uses:
Touchscreen allows a user to input commands into a computer by pressing or touching buttons / icons on the screen
Touch screens are used for self-service tills, e.g. petrol stations
They are often used for information Kiosks (booths) located in department stores, hotels, airports etc.
Used in Mobile phones and PDA
Used in ATMs
Advantages
Disadvantages
Very fast and easy to enter options
Limited number of options available on the screen
No training needed in order to use them (Easy operation)
Expensive compared to other input devices
No extra peripherals are needed except the monitor
Screen can become dirty and full of germs due to people touching it
Allows easy access to commands
Need specialized hardware and software
Difficult to vandalize
Are not suitable for inputting a large amount of data because they require a lot of arm movement
User need no knowledge of computer to operate them
people with disabilities can find them difficult to use
Can be made waterproof and so can be placed in open air e.g. on a station platform
Only items already on the screen can be selected (limited number of options available)
Touch screens are tamper proof
Using touch screens frequently can lead to health problems (e.g. straining of arm
Muscles, RSI, etc.)
Graphics Tablet:
Introduction:
It is a flat, rectangular, electronic plastic board on which a stylus writes or draws
The Operation system uses signals from tablet to work out the position of the stylus on the tablets surface
Each location on the graphics tablet corresponds to a specific location on the screen
Whatever written or drawn on graphic tablet can be seen on a computer screen and can also be save in the in the computer
Uses:
Graphics tablets are used by artists and designers to create and store digital graphics in a computer
It is mainly used for computer aided design and drafting by architects, mapmakers, artists and designers
Advantages
Disadvantages
A stylus can be pointed to different positions on the tablet quickly
A stylus and a graphics tablet normally have to work together, and cannot work separately
Much easier to draw images using a pen than it is to draw them using a mouse
Very expensive when compared to a mouse
Very accurate drawing can be produced
Not useful for some input needs such as entering data into the computer
Useful in countries where drawing and symbols are used instead of text
It may be difficult to match the position and motion of the stylus with those of the cursor on the screen
Enables operator to enter text and to draw pictures
Light Pen:
Introduction:
It is a pointing device that can be used directly with a CRT monitor
It can detect the presence of light
It is quite and old technology which can be used as alternative to mouse, touch screen and graphics tablets
They are used directly by drawing or selecting icons on a computer screen
They work by picking up light from the computer screen and then signaling to the computer exactly where the light was picked up. This allows the computer to draw on the part of the screen where the pen picked up the light
Uses:
Can be used as a pointing device
It is used for selecting objects
Can be used for direct drawing onto a CRT screen
Light pens are used by health care professionals (such as doctors and dentists) and aided design work
Advantages
Disadvantages
Using a light pen is more direct and precise than using mouse
Light pens normally requires a specially designed monitor to work with
Light pen is also convenient for applications with limited desktop space
Not as accurate as a graphics tablet when used for producing drawings
No typing skills are required for the user to operate them
Need much software to make it versatile
More accurate when used for pointing
Can be quite uncomfortable to use
Very small
Image Capture Devices:
The devices for obtaining a digital image from a vision sensor
Types:
Scanners
Digital camera
Digital Video Camera
Scanner:
Introduction:
It is a light sensing input device that converts printed text and graphics into a digital form that can be further processed by a computer
A scanner creates a digital photograph of a paper document
Many scanners also include OCR software, which can convert an image of text into a text file that can be edited
How it works:
Scanners reflect light off the hard copy in order to capture an analogue image of the document. The scanner then converts the received analogue data into digital format and then send the data into the computer which can be further processed.
Types:
Flatbed scanner
It works like a copy machine except that it creates a file of the document rather than a paper copy
The user places the paper document on the flat sheet of glass called the platen
It is larger, more expensive and less portable than handheld scanner
Handheld scanner
It can be manually passed over the image to be scanned
It is a portable device which we can use to copy an image from paper to our computer
They are ideal for capturing small images such as signatures and logos
It is smaller, less expensive and more portable than flatbed scanner
Uses:
Scanners are mainly used for image processing, which consists of capturing, storing, analyzing, displaying, printing and manipulating images
Are used to enter information on paper
Used to scan hard copy / printed documents into a computer
Photos can also be scanned into the computer
Advantages
Disadvantages
Very fast to enter hard copies into the computer
Scanned images are usually of lesser quality than the original document
Very easy to scan and store documents and images into computer
Scanned image can take up lot of disk space
Damaged photos can be scanned into the computer and stored
A Scanner is best for two-dimensional objects only
A scanner with OCR software can work as an OCR system
Digital Camera:
Introduction:
A digital camera takes pictures and stores the images digitally, rather than on traditional film.
They use flash, memory card, floppy disk and compact disc to store images
Most digital cameras have a built-in-screen
Digital camera image quality is measured in Megapixels. These are number if dots that make up the image
Most digital camera also capture video and sound as well as images
Almost all modern mobiles have built-in digital camera
Uses:
Used to capture digital images
Can be used for making videos
It can also capture sound
Advantages
Disadvantages
Save money for buying films
Digital camera are more expensive than ordinary films
Image can be reviewed
Photo printing cost is higher than that of ordinary film cameras
Unwanted images can be deleted
Camera users need to have computer skills to be able to transfer and print digital photographs
Image can be viewed on computer
Not all digital cameras produce high-quality image as traditional cameras
Film is not required which means producing photo is much quicker
Artistry of traditional photography us being lost
Memory cards can store thousands of photographs
Images can be transferred using Bluetooth
Web Cameras:
Introduction:
Web cameras are similar to digital cameras in there functions but they are directly connected to a computer and do not have memory storage
Web cam can produce both images and video
Images and videos are sent directly to the computer
Many modern computing devices (such as laptop) come with built-in-web cams
Uses:
Used for video conversation
Can be used as a security camera
Sometimes used to allow drivers to view the traffic conditions on the roads
Sued by parents to keep an eye on their children when they are in another room
Advantages
Disadvantages
Allow a long-distance face-to-face conversation
The image / video quality can be poor
Video conference business meetings and job interviews can be conducted very cheaply over a long distance
They dont have their own storage
Parents can keep an eye on their children
Are usually in fixed position (such as those on the portable devices) so cannot be easily moved
Can be left running constantly which makes them useful as security devices
Sound And Music Capture Devices:
Devices which can capture sound
Common Types:
Microphone
Microphone:
Introduction:
Microphones are used to input analogue sounds into a digital computer
The job of the microphone is to input analogue sound signals into the computer where the sound card which has ADC will convert analogue sound into digital signals. One Digitized, the sound can be stored and used by the computer
Speech recognition software ca recognize spoken words in a stream of sound data and convert them to text. It will be help full for those who are unable to type. But this software can be unreliable
Uses:
Used to input sounds \ speech
Used in voice recognition software e.g. converting speech into text
Hand-free mobile phones use a microphone to allow people to hold conversation without using hands
Used along with headphones in gaming so the gamers can talk to each other
Advantages
Disadvantages
Faster to read in text than to type it in using a keyboard
Sound files can take up a lot of computer storage speed
People with hand problems who cannot use keyboard can use microphone
Speaking words into a word processor is not as accurate as typing
It makes drivers safe as the drivers do not need to take their hands off the steering wheel in order to use their mobile phone
Background noise can interfere with voice recognition system
Microphone are very cheap to buy
Remote Control:
Introduction:
It is a small, hand-held device with a relatively small number of labelled command buttons
When the button is pressed the remote control sends a coded infrared or radio signal to the equipment
Uses:
Home entertainment system use remote controls. E.g. TV, DVE players
Industry uses remote control to operate machinery that might be too dangerous to get near to. E.g. Cranes with heavy loads
Advantages
Disadvantages
Device can be operated with having to go to them.
People with limited hand movement can find them difficult to use
Useful for people with disabilities as then do not have to move to operate them
The infra-red signal between the remote control and the device can be blocked
They can operate devices that are in an unsafe environment
It makes people lazy as they dont have to move
Devices and Methods for automatic data capture:
Devices and methods which can capture data without human involvement
Examples:
Optical character Recognition (OCR):
Optical Mark Reader (OMR)
Magnetic Ink Character Recognition (MICR)
Barcode Reader
Radio-Frequency Identification (RFID)
Magnetic Strip Reader
Smart Card Reader (Chip and Pin Reader
Biometric
Handwriting Recognizer
Optical Character Recognition:
Introduction
OCR consist of a scanner along with special software
It allows us to scan text on paper (hardcopy) into a computer. Once onto the computer, OCR software converts the scanned text into a digital format. Once converted to digital, the text can be used in programs such as word-processors, presentations, and websites
Uses:
Used in the processing of passports and identity cards
OCR is also used in the process of digitizing books
Also used in scanners
Advantages
Disadvantages
Very fast way of entering hard-copy text into a computer
The system can have difficulty in reading handwriting (especially if it is messy)
Cheap
Not 100% accurate
Avoid typing errors as the process is automatic
As it is not accurate, information needs to be manually checked for errors
It can read neat handwriting
Checking for errors is time consuming
Hard copies of documents can be read directly into a computer without retyping
User needs training to operate them
The character converted can be later edited by word processing software
Optical Mark Reader:
IT can read hand-drawn marks such as small circles or rectangles made on pre-printed forms in certain places
The OMR reader first reads the answer key sheer to record the correct answers based on the pattern of light and then reads the reaming documents and match their patterns of light against the answer key sheet
Uses:
Used to read shaded areas on documents
Used to read multiple chose examinations
Used to read Lottery tickets
Advantages
Disadvantages
Extremely fast way of inputting information into a computer
Forms need to be accurately designed to make sure that the mark / shading are in correct position to be read by the device
Very accurate
If forms have been incorrectly filled in they cannot be read properly
Can save money as there is no need to employ worker to enter form information into a computer
Can only read shaded areas (Cannot input or read text)
Has better recognition rate than OCR
Forms can jam in the machine as they are fed through
Large volume of data can be collected quickly and easily
OMR needs to be reprogrammed for each new document design
OMR readers are slow
The person putting the marks on the document must follow the instructions
Folding or dirt on a form may prevent the form from being read correctly
Magnetic Ink Character Recognition (MICR)
Introduction:
It is a system which can read information printed in a special ink
It is used to read the account number on the cheques. Then converts it to a form the computer can understand. The converted information is then send the computer so the cheque can be processed.
Uses:
They are mainly used to process cheques
MICR can also read customer account number and Bank sort-code
Advantages
Disadvantages
Cheques can be processed very quickly (up to 300 per minute)
Only a limited number of different characters can be read
Greater security than OCR because Special ink character cannot be changed
It is expensive
No manual input so lees errors
Magnetic Ink which it read is also expensive
Information can still be read even if someone writes over the magnetic ink characters
It is reliable
Barcode Reader:
Introduction:
Barcode reader uses laser beams to read bar codes
It reads a bar code by using light patterns that pass through the bar code by using light patterns
Once barcode has been scanned, a computer can read the information stored in the barcode and access details about the product that are stored in a database
Uses:
Used in supermarkets and stores where goods are marked with a barcode
They are used in libraries to scan library cards and read ISBN numbers on books
They are used in keeping track of packages that are being delivered to diffident locations
Also used in organizing luggage in airports
Advantages
Disadvantages
The process of data entry is fast and accurate
A barcode reader may misread a barcode if there is any or mark on the code
Barcode can be printed by normal printing methods
Only numbers can be coded
No need to write down price of the item on it
It need specialized software
Easy way of gathering information
Quite an expensive way of gathering information as each item need a barcode
Very accurate as there is no manual typing
It is also expensive
Enables automatic stock control
Bar code can be swapped on items which means that people may pay less for more expensive items
Radio-Frequency identification (RFID):
Introduction:
Radio-frequency identification (RFID) is the wireless use of electromagnetic fields to transfer data, for the purposes of automatically identifying and tracking tags attached to objects. The tags contain electronically stored information
With RFID tags we can reliably identify objects and track there movement
Magnetic Strip Reader:
Introduction:
Reads information from magnetic strips found on bank cards, membership cards and hotel door cards
Data on the card strip is read by passing the card through the magnetic strip reader. The magnetic strip then sends data from the card into the computer for processing
Uses:
ATMs use these readers to process the information on the bank cards
EFTOPS (Electronic Funds Transfer Point of Sale) use the readers to transfer customers money from their bank account when they purchase goods in stores
Hotel rooms sometime use them in place of door keys
Advantages
Disadvantages
Entering data is very fast. You just swipe the card through the machine
The magnetic stripe on the card can only hold a small amount of data
No data entry errors as no typing is involved
The cards need to be in contact with the reader in order to be used
The stripes on cards are not affected by water and are not easily damages
If by any possibility the card is damaged than all the data is gone
Data held on the card cannot be read by eye so bank details etc. are safe
Magnetic stripes on the cards are easily duplicated (Known as card cloning)
Easy to write fresh data onto the strip
It is not so serious if the guest leaves without returning the keycard, as the code ceases to be valid
Smart Card Reader (Chip And Pin Reader):
Introduction:
These allow people to pay for goods and services electronically at EFTPOS (Electrical funds transfer point of sale) terminals
The chip and pin reader works by inserting a bank / credit card into a slot and then entering a PIN (Personal identification number)
If the correct PIN is entered, the cost of goods / services will be taken from the card holders bank and transferred to the companies (Restaurant, Store etc.)
Uses:
Used to make secure payments for goods / services in stores
can be used as access cards for buildings and computer
The cards can store e-cash
It can store the holders medical records
Advantages
Disadvantages
Moe secure than magnetic strip readers as the user needs to know the correct PIN
Since the customer types in the PIN, they need to be careful that it isnt read by somebody else, thus giving an opportunity for fraud
Information on the chip is harder to clone (copy) than it is to copy magnetic stripes
It is possible to forget your PIN which means you cannot make payments with your card
Chips can hold more data than magnetic strips
Chip and PIN readers are portable
Chip and PIN readers provide a more robust system than magnetic stripe readers, since the chip does not need to be in contact with the reader
Biometric:
Introduction:
Peoples physical characteristics or behavior are known as biometric data which can be used for the purposes of authentication,
It can reads our unique body parts to recognize us. It can read our Fingerprint or our eyes
Uses:
Used for the purposes of authentication
Used to recognize someone by the unique body parts
Used on lockers
Used for safety purposes
Advantage:
Provide High security
More reliable than Chip and Pin readers and Magnetic strip cards
Handwriting Recognition:
Introduction:
It is a technique which allows a computer system to recognize characters and other symbols written by hand in natural handwriting
The technology is used for identification and also in devices such as PDA and tablet PCs
After one writes on a screen with stylus, the computer turns that persons handwriting into digital text
Uses:
Used in touch screen devices such as Mobiles
Also used in PDA and Tablet PCs
Advantages
Disadvantages
Handwriting recognition works regardless of which language text is written in
Cannot recognize mathematical symbols
It requires a little or no training to use
Only understand linear structure
It has very low system requirements and provides immediate input
IT is very tiring for arms
Handwriting needs to be clear for it to be recognized
Output Devices
Output:Output is data that has been processed into a used form called information
Output Devices:An output device is any hardware component that can be display information to a user. E.g. Printers, Monitors, Plotters, Multi-Media Projectors and speakers
Printer:
A printer is an output device that produces text and graphics on a physical medium such as paper,
Printer information is often called hard copy because the information is exist physically and is more permanent form of output than that on a Monitor
Printing speed of a printer is usually expressed in pages per minute
Printers can be grouped into:
Impact Printer
It forms characters and graphics on a piece of paper by striking mechanism against an ink ribbon that physically contacts the paper. E.g. Dot Matrix Printer
Non-Impact Printer
It forms characters and graphics on a piece of paper without striking the paper. E.g. Laser Printer and Ink-Jet Printer
Factors affecting print Quality:
Dots per inch
It is a measurement of printers resolution indicating how many dots can be placed by the printer in one square inch. The larger the number, the higher the resolution.
Types of Printer
Each type of printer has its own capability of printing. Some types of printers produce high quality prints while others produce low quality.
Print Mode
The printing mode may also affect the quality, For example the draft mode increases the print rate but quality is reduced
Toner:
The quality and amount of toner also affect the print quality
Advantages
Disadvantages
Information produced is permanent
The time to get the printout is slow, when compared with display devices
Paper is wasted for obtaining the output. There is no wastage of paper in Monitors
Printers are generally noisier than display devices
Dot-Matrix Printer:
Introduction:
It is an impact printer that produces printed images with a print head striking mechanism
Most dot-matrix printers use continuous-form paper (It can make carbon copies of a document using special Carbon paper)
A higher number of pons on the print head means more dots are printed, which results in higher print quality
Its speed is normally measured by the number of characters per second it can print. Its speed is usually 30-550 characters per second
How it works:
These printers work by using a set of pins to press an inked ribbon against paper. There are 9-24 vertical column pins in a rectangular print head. When the pin / Ribbon hits the paper a printed dot is left behind. The dots can be arranged to form basic text and images. Different colored ink ribbons can be used to produce colour printouts.
Uses:
They are very robust and can be used in noisy and dirty environments (like garages and warehouses)
Used for printing bills in ATMs and stores
Used in banks
They are also used as cash registers
Used for data logging
Advantages
Disadvantages
Work fine in dusty and dirty environments where laser or inkjet printers could easily be damages
Very noisy so not suitable for an office environment
Carbon copies can be produces using carbonated paper
Very slow to print (slowest of all the types of printer)
Very cheap to buy (Most cheap printer)
Very poor print quality (low resolution)
Very cheap to maintain (repair)
Colour printout is limited
Good for continuous printing
The pins get bend easily
It can print multipart forms
Colour looks faded and streaky
Energy efficient
Heavy and bulky so they take lots of desk space
Reliable (durable)
Ink-Jet Printer:
Introduction:
It is a non-impact printer that that forms characters and graphics by spraying tiny drops of liquid ink onto a piece of paper
Ink-jet printers can produce text and graphics in both black-and-white and colors
Some ink-jet printers can print photo-quality images on any type of paper
Printer resolution is measured in dots per inch
It has a resolution of 300 dots per inch
They have small amount of internal memory (RAM) to store print jobs so printing is done a bit at a time
How it Works:
Inkjet printers work by spraying ink into a page of paper. The ink is held in ink cartridges and there are 4 different colours Black, Cyan, Magenta and yellow. Motors are used to position the ink cartridge over the correct position of the page and to drag the paper through the printer.
Uses:
Good where few print outs are needed e.g. in homes
Often used to print photographs
Also used in offices
They are often used for manufacturing colour filters for LCD TVs
Used for Textile Printing (Printing of Fabrics)
Advantages
Disadvantages
Inkjet printers are generally quiet
Specialized papers are required to produce high quality colour output
fast than dot matrix
The ink cartridges and specialized papers are expensive
They can produce high quality colour output
The ink may smear when printed on ordinary paper
Much cheaper to buy than laser printer
It is prone to clogging and damage
Smaller than laser printers so take up less space
Slow printing rate
Do not produce ozone or other harmful compounds
Ink cartridges dont last long
Very quiet whilst printing
Ink cartridges are expensive to buy
Capable of printing in vivid colour
Printouts can easily smudge if document is not left to dry properly
They take less space than laser printer and dot-matrix printer
ink cartridge can dry out if not used for long time
They require no warm up time
Even one drop of water can cause blurring
Laser Printer:
Introduction:
Laser printers are the non-impact printers which are also known as page printers because they process and store the entire page before they actually print it
They use toner pressed on a page to produce printed documents
The mechanism of how a laser printer works is similar to a photocopier
Most laser printers today can print text and graphics in very high quality resolutions, ranging from 600 dots per inch to 1200 dots per inch (dpi).
They can print text at a speed of four to over thirty pages per minute
They use buffer memory which stores the information for the whole documents before the pages can be printed
How it works:
Laser printer work by using laser beam to draw onto a drum. A special power known as toner is sprayed onto the drum and it sticks to the parts that contain the positive electric charge. The drum is then pressed onto a sheet of paper and the paper is heated (fused) so that the toner is bound to the paper.
Uses:
Very useful for printing where noise levels need to be kept low
Used in good environments where high volume of printing is required
Used for mass production
Used when high quality of printing is required. E.g. used in offices, schools
Advantages
Disadvantages
Laser printers are generally quiet and fast
The initial cost of laser printers can be high
They can produce high quality output on ordinary papers
Laser printers are more expensive to buy than dot-matrix printers and ink-jet printers
They cost per page of toner cartridges is lower than other printers
Environmentally unfriendly as it produce ozone
Toner cartridge can last a long time (Toner is waterproof)
Use more power than inkjets
Laser printers can handle high volumes of printing
They are larger in size compared to other types of printers
Reliable dont breakdown as easily as inkjet printers
Toner is toxic
Cheaper to run than inkjets (low cost per page)
It is expensive to repair
Colour printing is possible
Monitors:
A monitor is an output device that displays information from a computer on a screen
Types:
Thin Film Transistor (TFT)
Liquid Crystal Display (LCD)
Cathode ray tube (CRT)
Advantages
Disadvantages
The output is immediate and visual
The output does not last long, when the display changes the previous output is lost
Thin Film Monitors (TFT):
Introduction:
These are thin flat screened monitors that are commonly seen today
As they become cheaper, these have taken over from CRT monitors as the most popular computer screens
TFTs are used with the newer desktops such as PCs, laptops and mobile phones
How it Works:
TFT screens are made up of thousands of tiny pixels. Each pixel has 3 transistors red, green and blue and each transistors can produce different intensities. This allows huge amount of colours to be produced (16.7 million). A back light is used to shine light onto these pixels in order for the colours to be produced. In order to light a single pixel, tiny windows can be opened and closed to allow the light to pass through and onto the pixel.
Uses:
TFT monitors are mainly used in portable computers like laptops and mobile phones
Are also used by gamers in home
Now a days this monitor is mainly used
Advantages
Disadvantages
Lightweight so they are perfect for portable laptops and wall mounting
Images can appear un clear when viewed from an angle (you have to look straight at the screen for the best image)
They are very thin and do not take up as much desk space as a CRT monitor
Lower picture quality compared to a CRT
They produce much less glare than CRT and so are friendly to eyes
Cannot be used with light pens yet
They use less power than CRT monitors
They produce less heat than CRT
They emit less radiation than CRT monitors
Liquid Crystal Display (LCD):
Introduction:
An LCD is thin screen which has a backlight behind a grid of tiny liquid crystal pixels
They are replacing CRT
How it Works:
An LCD monitor has a backlight behind a grid of tiny liquid pixels. A computer graphics card can supply a stream of digital data to LCD monitor. The DAC in the monitors control programs electronically scans all the pixels and then delivers an individual analogue signal to each pixel. The analogue signal control how much light of a certain colour the pixel allows through from the backlight. The display is formed by light shining through the gird of thousands or even millions of pixels.
Uses:
Used in homes, offices
Used in laptops
Also used in PDAs, Media Players and Mobile phones
Advantages
Disadvantages
They are small and easy to fit on a desk
He image can only be viewed from a relatively narrow range of angels
They are light and easy to mount on walls
They can display a relatively limited range of colour and brightness
They are compact enough to fit to laptops, PDAs, Media players and Mobile phones
Manufacturing defects can cause permanent lit or unlit pixels
There is relatively little reflection of ambient light from the screen
The stability of the display and absence of flicker make for more comfortable viewing
Cathode Ray Tube (CRT)
Introduction:
They are the old, Bulky, Heavy monitors that are still used today (although being used less and less)
There are the least expensive type of monitor
CRT are becoming rare as LCD and TFT monitors are replacing them
How it Works:
CRT produce an image (made up of tiny dots) by firing Electron beams against a phosphor screen. Each dot is colored Red, Green or Blue of different intensities which produces a vast amount of different colours. The dots combine to create millions of different colour shades.
Uses:
CRT are used with light pens to allow drawing to be created on the screen
Used in homes
Used in TVs
Used in Cathode Ray oscilloscope
Used as display device in radar
Advantages
Disadvantages
Can be used with light pens to create drawing on screen
They are very large and bulky with means they take up large amount of desk space
Produces a larger range of colours than TFT monitors
They create a lot of head and have been known to cause fires
The screen angle is better than with TFT
Screen glare when in direct light viewing difficult
Cheaper to buy than TFT
They also need more power than TFT to operate
It has Multiple resolutions
It is more rugged (harder to damage)
Much better viewing angles than most of LCD
Higher refresh rates
Plotters:
Introduction:
They produce hard copies but are capable of printing on a very large pieces of paper (e.g. 3 foot wide by 10 foot long)
Plotters can also produce very large and accurate documents such as blueprints (plans) for buildings
Plotters draw images on the paper using colored pens which are moved around the paper by a computer
Pens can be replaced with cutting tools to produce large signs
Two types:
Flatbed plotter
Drum plotter
Uses:
Used to produce large, accurate drawings
Used to draw Blueprints of Buildings, Maps, Giant posters and adverts
They are ideal for Computer aided design (CAD) technical drawings and architectural design
They are widely used in Architect, Engineering and construction (AEC) and geographical information system (GIS) sectors
Additionally, they are used by adverting agencies and print and design shops
Advantages
Disadvantages
They can produce much larger printouts than other printers
Their print times are very slow
The print quality is extremely high
They are very expensive to buy and maintain
Plotters can also cut out designs for use in sign making
They take up more space than regular printers as they are huge
They are able to work on large sheets
It can print on wide variety of materials including sheet steel, plywood, aluminum etc.
They are efficient, reproducible accurate and fast
They can save all patterns and templates on disk and eliminate the hassle of having to load the same patterns of a plotter
Drum Plotter:
Introduction:
A drum plotter may also be called a roller plotter
It consists of a roller or drum that rotates back and forth to reproduce the image
How it Works:
The Drum Plotter prints by moving a pen on a piece of paper. It can only print simple graphics and it prints very slowly because of the mechanical movement of the pen. The type of pen used affects the speed of the printing. A typical pen uses a cellulose fiber rod inserted through a circular foam tube saturated with ink, with the end of the rod sharpened into a conical tip. The ink pens are held by the robotic drawing arm that moves side to side as the roller, as the roller which holds the paper or material moves back and forth. This results in production of high quality graphics and images.
Uses:
Plotter is used for printing very large graphics and are therefore used in billboards, maps etc.
They are mainly used in medical environments to plot medical information.
Flatbed Plotter:
Introduction:
The flatbed plotter, also known as the table plotter, draws on flat sheets that are spread and fixed on a rectangular flatbed
How it Works:
This type of plotter has two drawing arms, each with its own set of pens. The drawing arms moves over the fixed sheet of material and produce the desired image. Flatbed plotters use a system where the paper is fixed, and the plotter moves a pen up and down, and left and right to draw the required marks on the paper.
Multi-Media Projectors:
Introduction:
They are usually controlled using a remote control
The remote control makes it possible to direct the presentation without the need to be at the computer
Multimedia projectors are often hung from the roof in special brackets
Uses:
can be used for training presentations to allow the whole audience to see images from a single computer
Also used for large scale advertising of new products
Used in home cinema system where images from DVDs or televisions are projected to a large screen
Used for advertising
Can be used for playing games
Advantages
Disadvantages
Large-sized picture so provide a clear view
Lower image quality compared to a computer screen
Enhance the viewers experience
Very expensive to buy
It saves space as it is small in size
Cooling fans in the projectors are noisy
It is easy to install
It does not work well in low light
They are available in variety of sizes
The maintenance cost is high as the lamp of a projector needs to be replaced occasionally
Projectors are designed to be highly compatible with laptops, memory cards and other electronic devices
It has either no audio of its own or has very little sound
Remote controls and other features make it easier for the presenter to interact with the projector
It requires more energy
Speakers:
Introduction:
To provide sound output, the computers sound card has a DAC to produce an analogue output. The computer also needs at least one speaker
The speaker allows the user to hear the sound
Speakers can be connected directly to a computer or are built into the monitor or casing
Headphones are a version of speakers for personal use. They are often used in environment where other people should not hear the sound produced. This might be because it would disturb their concentration.
How it Works:
Speakers are analogue and cannot output digital computerized sounds. Digital data from the computer must first be converted into analogue sound using a sound card. The analogue sound can then be output via the speakers and we can listen to it.
Uses:
Used to output sound from monitors
Used in home entertainment
Used in TVS
Used by blind people to listen to words on the screen
Can be used to play music files
Advantages
Disadvantages
Everyone in the room can hear the sound
Output from speakers can disturb people trying to work
They can help blind people use a computer because text can be turned into sound
High quality speakers can be expensive
High sound can cause ear damage
Computer Sciences Notes By Samee Arif