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Computer - Marcador
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| What is a 2D scanner ? | A 2D scanner converts documents into 2D images that input to a computer |
| Give two applications of 2D scanners | 1)Scanning passport images for facial recognition The passport image is scanned in and then compared with a digital image of the passenger taken by a digital camera. 2) Updating passport information on at the airport using optical character recognition |
| What is a 3D scanner and state two places where it is used? | Medical imaging using xray MRI scanners using radio scanners |
| What is a barcode ? | Set of line of different thickness that represents different numbers |
| What are the applications of barcode? | Supermarket billing Recording attendance in a company |
| What are the contents of a barcode reader? | Country of orgin Manufactures code Serial number |
| What is a pointing device? | A device used to move the pointer on the screen |
| Name four pointing devices | Mouse Joystick Tracker ball Touch pad |
| Give one disadvantages of the mouse | Takes space to operate |
| Give two advantages of joystick | Takes less space to operate Faster to move |
| Where are joysticks used ? | Mainly in gaming |
| Give an advantage of tracker ball | Takes less space than mouse |
| Give two places where tracking ball is used | Wheelchairs Operating CCTV cameras |
| Give an advantage of the touch pad | Takes less space to operate |
| Where are microphones used? | Online conferences |
| What is voice recognition, how does it work, where is it used? | A person is recognized by his voices when he speaks into a microphone It works by converting a recording of person's voice into a digital form and stores it into the the computer, when someone speaks into the microphone another digital pattern is created which compared to the stored pattern. Security systems which require to identify the person |
| What is speech recognition? | A computer recognizes words spoken into the microphone and performs tasks according to the word spoken |
| What are the drawbacks of speech recognition? | Background noises will confuse the system Different people will have different accents\punctuations Recognition is slow |
| Where is speech recognition used? | For disabled people Operating a mobile device Dictating words to a word processor |
| How does speech recognition work? | Each word spoken into the microphone is broken down into its individual phonems, then a dictionary of phonems is searched for the same combination of phonems and word is recognized |
| What is analog data? Give examples | Data which gradually changes from one state to another Sounds Temperature Speed |
| What is digital data? Give an example | Data which changes from one state to another without any intermediate stages Switch |
| What is a monitoring system? Explain how it works | Measures a variable in its enviroment and compares it with the range of stored values and if it is outside the range it will warn the user Sensors send readings to the analog to digital converter at regular intervals The ADC converts the analog signals to digital so that it can be processed by the microprocessor and then sends it to the microprocessor The microprocessor compares the readings to the maximum and minimum stored value If the reading outside the acceptable range a warning message is sent or an alarm is activated |
| Give three places where monitoring systems are used | Monitoring heart rate of a patient in a hospital Temperature level in car engine Burglar alarm |
| What is a control system? Explain how it works | Measure a variable in its enviroment and takes action to maintain the variable in the acceptable range The sensor send readings to the analog to digital converter at regular intervals The ADC converts the analog signals to digital so that it can be processed by the microprocessor and sends it to the microprocessor The microprocessor compares reading with the maximum and minimum value If the readings are within the range a signal is sent through the digital to analog converter to switch off the actuator If the readings are outside the acceptable range a signal is sent through the digital to analog converter to switch on the actuator |
| Give three advantages of hard copies | Permanent Portable Easier to make copies |
| Give an advantage of soft copy | Can easily be edited ( Suitable for output that is continuously changing) |
| What are the advantages of audio outputs? | Attracts users attention Suitable for disabled(blind) Many people can be given the mess |
| What is an actuator? | A computer controlled device which can change its enviroment |
| What is a MIDI file? | Musical Instrument Digital Interface A MIDI file contains instructions on how to play music MIDI file is read by sequencer software on the computer Computer is connected to a MIDI interface(Device) MIDI interface is connected to music instruments such as electric drum, electrical guitar The sequencer software translates each MIDI instructions to musical instrument, processes and sends it to the instruments through the MIDI interface Musical instrument plays the music Can connect up to 16 channels (Devcies) |
| What are the advantages of MIDI files over mp3 | Smaller file Easier to edit |
| What are the disadvantages of MIDI files over mp3 | Special hardware |
| What are the advantages of barcodes in supermarket ? | To the company Automatic stock control Less cashiers so saving money Less errors in billing To the customer Less waiting time More detailed |
| What is QR (Quick Response) code? What are the items stored in QR? | A set of black dots on a white background, which can store up to 7000 characters URL Phone number Address of the vendor |
| What are the advantages of QR codes? | A special reader is not required (Any digital device with a camera is suitable) Larger capacity than barcodes Scanning can be done from a distance |
| Name the four different type of keyboards and give a small description for each | QWERTY Names because of the first line of key is qwerty Ergonomic A keyboard designed to prevent RSI( Repetetive strain injury) Concept keyboard Keys are printed onto a thin sheet of plastic Normally used in pubic places such as self service restaurants, ATMs and in appliances such as washing machines and microwaves Easier to clean Easier to use since they keys can be different shapes, color, sizes Braille keyboard A keyboard used by blind people |
| What are the disadvantages of 3D printers? | Violation of copyright leads to unemployment People will have access to dangerous technologies |
| Where are infrared used? | ATM Ticketing system Medical equipment |
| Where is capacitive touchscreens used? | Mobile phones |
| What are the disadvantages of Infrared? | Dust particles may produce incorrect touches Moisture and water will affect the proper working of the screen |
| What are the advantages of infrared touchscreens ? | Less affected by scratches on the surface of the device You can use use it bare finger, gloves and stylus Multitask is possible |
| How does a infra-red touch screen work? | A grid of infrared light sources and sensors are used to detect where the person touches the screen, when the screen is touched the infrared light beam is interupted and the location of the touch can be identified |
| What are the disadvantages of resistive touchscreens? | Not durable Not multitouch Not very clear in bright light |
| What are the advantages of a resistive touchscreen? | Cheaper You can use bare fingers, stylus or glove |
| How does a resistive touchscreen work? | Consists of a polyester sheet below which there is a glass sheet. When a person touches the screen, the polyester screen touches the glass and the circuit is complete. When it is complete, the microprocessor can identify where the screen was touched |
| What are the disadvantages of capacitive touchscreens? | Only works when touched by hands, stylus and capacitive gloves |
| What are the advantages of capacitive touchscreens? | Cheap Durable Visible in bright light Multitouch |
| How does capacitive touch screens work? | It contains several layers of glass with electricity flowing between them, when a person touches the screen the electricity in that area passes out of the device through the body This change is detected by the microprocessor to identify where the screen was touched |
| What are the three types of touchscreens ? | Capacitive Resistive Infa-red |
| What are the disadvantages of projectors? | Lower quality than monitors Time consumed to set up the projector |
| What are the advantages of projectors? | Portable Larger audience Adjustable screen size |
| What are the advantages of OLED? Give two applications | Less electricity consumption No backlight(thinner) Bendable Mobile phones Advertising screens |
| What are the advantages of LED ? | Brighter picture Less electricity consumption Shorter time to reach maximum brightness Longer lifetime |
| What is OLED? | Organic material embedded between metallic rocks which glow when supplied with electricity |
| What does an LED do? | An LED backlight is used to emit light on the LCD panel |
| How does a LCD work? | Uses a Cold Cathode Flourescent Lamp(CCFL) to emit light onto a grid of liquid crystals |
| What are the materials that can be used by the 3D cutter? | Glass Jade Metal Wood Polymer |
| What is a 3D cutter? | Device used to create 3D objects by cutting away material from a block, they are capable of cutting designs inside the object. |
| What is a 2D cutter? | Device used to engrave characters on a flat surface such as nameplates, tombstone, wooden furniture |
| What is subractive manufacturing? | The object is created by removing parts of the material until object is formed. |
| What is additive manufacturing? | Creating three dimensional objects by adding materials layer by layer (All 3D printers are additive) |
| What are the three type of monitors? | LCD(Liquid Crystal Display) LED(Light Emitting Diode) OLED(Organic Light Emitting Diode) |
| What are the advantages of 3D printers ? | Can manufacture products much faster Products manufactured are cheaper |
| What materials can be used by 3D printer? | Ceramic Metal Resin Wood Granite |
| What is a 3D printer ? | A device which produces three dimensional objects |
| Give four differences between ink jet and laser printer | Laser printers use toners , ink jet uses cartridge Laser printer is faster Laser printer has better quality Laser printer is used for larger quantities |
| Give three features of the laser printer | Uses dry powder ink Uses static electricity to produce text and images Prints the whole at one go |
| What are the four main parts of a ink jet printer? | A print head which consists of nozzles which spray ink onto the paper to form characters An ink jet cartridge for blue, yellow, magenta and black cartridge or single containing all Stepper motor and belt which moves the print head from side to side across the page A paper feed which automatically feeds the printer the pages |
| How does a peizoelectric printer work? | A crystal is located at the back of the ink reservoir for each nozzle. The crystal is given a tiny electric charge which makes it vibrate, which causes ink to be ejected on to the paper. Simultaneously more ink is brought in The process is repeated till the printing cycle is complete |
| How does a thermal bubble printer work? | Tiny resistors create localised heat which makes ink vaporise , which causes the ink to form a tiny bubble, which expands causing the ink to eject out of the printhead When the bubble collapses, a vacuum is created causing fresh ink to be drawn into the printhead The process is repeated until the printing cycle is complete |
| What are the two types of ink jet printers? | Peizoelectric Thermal bubble |
| What are the two types of printers? | Ink jet printers Laser printers |
| Give three disadvantages for audio output | Disturbs the enviroment(Not suitable for enviroment such as hospitals and libraries) Cannot be heard in noisy enviroments As message is not permanent it has to be repeated |
| Give four advantages of Audio outputs | Suitable for disabled people(blind) The output is given to many people simultaneously Attracts the user User can be far away from the system |
| Give an advantage for softcopy | Easier to edit( Used for outputs that are continuously changing) |
| Give three advantages of hardcopy | Permanent Portable Easier to make copies |
| What are the advantages of DRAM and where is it used? | Cheaper Uses less power Larger capacity RAM in PC |
| What are the two types of secondary storage? | Solid State Drive Hard Disk Drive |
| What are the three magnetic storage deices ? | Hard disk Magnetic tape Floppy disk |
| What is latency ? | Time taken for specific data track to rotate around to the READ-WRITE head |
| What are the two types of SSD? | Flash memory EEPROM ( Electrically Erasable Programmable ROM) |
| What are the features of Flash memory? | Uses NAND gates Cheaper Only one block of data is read or written at a time Majority use this Non-Volatile Rewritable Memory |
| What are the features of EEPROM? | NOR gates Faster Expensive Single Byte of data can be read/written at a time |
| What are he advantages of SSD over HDD? | More reliable No latency therefore faster Lighter and thinner Produces less heat and less power |
| What is an offline storage? | Non- volatile storage devices that can be easily disconnected from computer and stored in a different location |
| Give four examples of offline storages | CD/DVD/Blu ray ( Optical Drives) Pen drive ( solid state) Portable SSD ( solid state) DVD - RAM |
| How is data written into an optical device? | 1)A laser is shone onto the surface of the disk, the surface is normally covered with a thin aluminium layer. 2) The laser burns pits into the Aluminium, the surface is then covered with pits and lands representing 1s and 0s ( data is written to a single spiral track) |
| What are the storage sizes of CD, DVD, Blue Ray | CD- 650MB DVD- 4.5GB -9GB Blu Ray- >50GB |
| How does lossless compression work? | Repeating characters are identified The replaced with a smaller code A key is added at the end of the file |
| Explain why should a SD card be properly disconnected before removal? | NAND gate memories write one block at a time, disconnection ensures that last block of data is safe, if it is not disconnected before removal the file maybe corrupted |
| How is data transferred from SD cards to the computer? | 1)Connect the device with the card to the computer using a USB cable 2) Transfer the data using a bluetooth connection between the device and the computer 3) Use a SD card reader |
| What are SD( Secure Digital) / XD( Extreme digital)? | Used to store data in mobile phones, digital cameras and MP3 players |
| What are the features of memory sticks( Pen drives)? | Portable Used for temporary backups to move data from one device to another Used as security dongle |
| Why can READ or WRITE be done one at a time with DVDs | Since it has only one track |
| What are dual layer DVDs? | A DVD which has two layers to which data can be written |
| What is birefringence? | A problem caused in dual layer DVDSs due to the reflected light from the second layer |
| How is data read from an optical device? | The laser is shone onto the surface The reflected light is captured by a light sensor The amount of light captured for pits and lands are different This is used to recognize between 1s and 0s |
| What are the features of a DVD-RAM? | Concentric tracks therefore possible to READ and WRITE at the same time Lasts longer than a DVD or a CD Has two layers of polycarbonate |
| What are the feature of a blue ray ? | Uses blue laser which has a shorter wavelength Therefore: Smaller pits; Higher pit density; Increases capacity Has a method of encryption which prevents piracy Higher transfer rate |