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33 Cards in this Set
- Front
- Back
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Bit
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The smallest unit of computer memory holding 1 or 0
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Byte
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Binary number made up of 8 bits
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ASCII
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•A way to store characters as numbers
• Uses 7 bits to store a number between 0 and 127 |
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UNICode
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A character table that uses 2 bytes per character
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Binary coded decimal
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A coded numeric string using 4 bits
used in calculators, cash machines etc. |
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Two's Complement
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A way of representing negative numbers in binary where the left most bit is made negative
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Pixel
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• PICture ELement
• A single square of colour that makes up an image The smallest possible addressable area defined by a solid color, represented as binary, in an image |
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Image resolution
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The number of pixels in the width and height of an image
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Screen Resolution
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The number of pixels in the width and height shown in your screen
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File header
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•Where image resolution is found
• May also contain info about how many bits are used to store each pixel |
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Monochrome Image
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A byte can store 8 pixels
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16 Colour Image
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4 bits required for 16 possibilities
A byte can store 2 pixels |
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256 Colour Image
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A byte can store 1 pixel
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24-bit Colour (True Colour) Image
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Each pixel is stored using 3 bytes (Red, Green and Blue) giving us 16.7 million colours
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Vector Graphic
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•A graphic recorded by storing the geometrical information to 'draw' the shapes
• There are no pixels |
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Drawing object
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•A distinct, selectable shape that makes up a vector graphic
e.g. square, circle, bezier curve line |
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Property (of vector graphic) |
A value assigned to the drawing object to set its characteristics
e.g. Fill colour, line colour, line thickness, x and y coordinates, shape. |
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Drawing list (vector graphic)
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• A list of drawing objects
• There is an order that determines which shapes will 'on top' of others |
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Sampling
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Taking a reading at a point in time
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Sampling rate
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How often we take a reading
(typical sampling rates range from 11 to 44.1kHz) |
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Sampling resolution
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•Number of bits used to represent the vertical axis on the graph
• An 8 bit resolution provides a 'precision' of 256 values • A 16 bit sample resolution provides a 'precision' of 65,536 values |
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Video
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Moving images
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Frame Rate
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Number of images being displayed per second
(Usually 24fps) |
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Interlaced Video
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Displays alternate horizontal lines
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Progressive Video
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Displays a whole frame at a time
Superior to interlaced |
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Temporal Redundancy
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Looks for data that doesn't change between frames
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Spatial Redundancy
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Looks for data within the frame that may be redundant, that is repeating patterns or similar pixels
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Lossless Compression
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•Exactly the same before compression and after decompression
•No loss of information |
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Lossy Compression
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Some data is discarded during compression
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Run Length Encoding
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Replaces sequences of the same data with a count of that data |
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Container format
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Wraps around the video data providing thereader (reading program) with information about the video data such as theresolution, frame rate, compression algorithm used, etc. There will also be audio data in a video fileand information relating to how the audio is stored and synchronised with thedata file should be present. AVI, WMP, MPG, DIVX, XVID forexample. |
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Analogue to Digital Converter (ADC) |
Converts analogue sound into digital signals that can be stored on a computer
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Digital to Analogue Converter (DAC) |
Converts digital signals stored on a computer into analogue sound that can be played through devices such as speakers
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