Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
23 Cards in this Set
- Front
- Back
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Key board
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•Has its own processor and circuiting
•Makes up key matrix (a grid of circuits underneath keys) • Each circuit is broken below the key that pressing the key closes and allows current through • When a circuit is closed, the location is compared to the character map in ROM • When a key is pressed, info maintained in the memory buffer until used |
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Tracker Ball Mouse
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• Ball touches desktop, two other balls touch the main ball and track the x and y directions of the main ball
• Balls connected to a shaft which spins a disk • Disk has holes which show and break the connection between an infrared LED and sensor • Pulses of light directly relate to speed and distance moved by mouse • A processor chip in the mouse converts pulses to binary data to be sent to the computer |
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Laser Mouse
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• LED bounces light off the desktop into a CMOS (complimentary metal-oxide semiconductor)
• CMOS sends images to a DSP (digital signal processor) in the mouse • DSP detects differences in images to determine how far and fast it has moved in what direction • DSP sends vector to the computer • Cursor on screen moves according to vector |
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CMOS
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Complimentary metal-oxide semiconductor
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DSP
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Digital signal processor
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Scanner
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•Page is placed on the glass plate, scan head passes across page
• A lamp lights up the document and a series of mirrors and lenses bounces the light to the light sensory array • The brighter the light reflected, the greater the electrical charge • Lens splits the image into three colours and electrical charge is measured • electrical measurements converted to binary code which can then be represented on a computer as an image. |
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Inkjet Printer
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• Document converted to bitmap image
• Print head moves across page as page is rolled through the printer • Print head has thousands of tiny nozzles with ink in them • A tiny element inside each nozzle heats the ink enough that it expands and one drop of ink falls onto the page • There are rows of nozzles for each colour of ink and they are timed to fall exactly in the right place |
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Laser Printer
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• The primary charge roller rotates applying a negative charge to the OPC drum
• A laser projects the image of the document onto the OPC drum, positively charging those areas • Toner stored in the hopper is moved around, becoming negatively charged and becoming attracted to the positively charged areas on the OPC drum • Paper rolled onto the OPC drum and toner is transferred onto the paper • Then it passes through the fusing assembly where it is melted and fused onto the paper |
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Speaker
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• Electrical signals > Physical vibrations
• A driver rapidly vibrates a cone • The wide end of the cone is attached to a suspension which is a flexible rim connecting the cone to the basket • Narrow end of the cone is attached to the voice coil by a spider • The voice coil is an electromagnet, current in the coil changes direction, the magnet's polar orientation changes, moving the cone and producing a sound wave |
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Hard Disk
(Reading) |
Reading:
• Platter spins around the spindle • Data requested from an area on the platter by the computer • Actuator arm moves the read head to that track • Data is read by the data sector spinning under the read head • Read data is sent from the IDE connector to main memory |
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Hard Disk
(Writing) |
Writing:
• Platter spins around spindle • Data to hard disk using IDE connector • Actuator arm moves write head to the track • Data sector spins under write head and data is written |
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Flash memory
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•USB put into computer
•Driver loads telling the computer the code needed to read and write to it •USB is read giving the computer info on the file allocated table •User data request is sent to the USB port and USB returns data requested |
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Optical Disk (CD ROM)
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•A single track runs in a spiral pattern from the center to the outside, made of pits and lands
• A low powered laser is shone on the surface, reflection captured in a photo diode sensor • pits and lands represent 1 and 0 • Disk spins and laser follows track • Binary data is then sent to the computer |
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Optical disk (CD-R)
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•Made of a reflective metal disk with a layer of green, opaque dye on top
•A high powered laser is shone onto the CD-R, changing the transparency (permanently) of the dye above. Transparent and opaque parts represent 1 and 0 • disc spins and the laser follows the track, putting the binary data onto the CD-R in a spiral track R: laser is shone and reflection captured in photo diode sensor |
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Optical disk (CD-RW)
re-writable |
A high powered laser is shone onto the CD-ROM, depending on whether this is very high powered or heats at a slightly lower temperature, the top layer of metal cools differently. these will result in different amounts of reflectivity, which represents 1 and 0
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Sensor
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Detects movement or other characteristics from the environment and turns them into electrical signals
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Actuator
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A type of motor that is responsible for moving or controlling a mechanism or system
Converts electrical signal into motion |
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RAM
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•Random access memory
•Contains instructions and data for CPU to process •Volatile (empties at power off) Randomly accessable |
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ROM
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•Read only memory
•Not volatile •Unchangeable •Provides CPU with instructions Randomly accessable |
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SRAM
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•A flip flop made of 4 or 6 transistors
•Doesn't need refreshing •Faster than DRAM •Takes up more space •More expensive than DRAM Used for CPU's speed sensitive cache |
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DRAM
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•Made of transistors and capacitors
•Holds one bit •To store a 1 the capacitor is filled •To store a 0 the capacitor is emptied •CPU or memory controller recharges the capacitor before discharge. Memory controller reads the memory and writes it back •Takes time and slows memory •Larger system RAM space |
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Primary storage
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•High speed because its connected directly to the CPU
•Volatile - requires an electrical current e.g. RAM, cache |
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Secondary Storage
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•Not connected to the CPU
•Not as fast •Retains data when computer turns off because it stores data magnetically e.g. Hard drives, optical drives |
