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Comp Sci Paper 1 - Coggle Diagram
Comp Sci Paper 1
Units and File Sizes
Bits are the smallest measure of data, one bit represents a 0 or a 1
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Storing Images
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Colour depth is the amount of different RGB (Red, Green, Blue) that a pixel can have, a higher colour depth will result in larger amount of possible colours
2 bit images can have a colour depth of 2 (to the power of 2) with the integer representing a 1 or 0 and the indices representing the number of bits per pixel.
Resolution is the density of pixels in an image, a greater density results in a better image quality but also filesize.
Storing Sound
'Analogue' sound needs to be converted into digital data for a computer to be able to read and store it
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Sampling rate is frequency of which values are taken as samples, this assists the computer in reading the sound
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The sound quality will increase if sampling rate increases. However bit rate will also increase and henceforth file size too.
Secondary Storage
There are three types of secondary storage: Magnetic, Solid State and Optical
Magnetic storage devices (such as hard disk drives) have a large capacity and are reliable. They have moving parts however so are not particularly portable.
Solid state devices (such as a USB drive) are fast, reliable and portable with no moving parts. However they have limited read / write cycles.
Optical devices (such as CD's) have a low cost per GB and are relatively portable. Though they also have a low capacity and can be easily scratched.
Virtual memory
Stores not currently used data, not currently used instructions and not currently used parts of the operating system
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When the user wants to use data stored inside virtual memory, data from the RAM has to replace the data in the VM
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Compression
Compression is the process of decreasing a file's size while attempting to make the compressed file as similar to the original as possible
"Lossy" compression is a form of compression that majorly reduces file size. However, using this compression also results in a loss of data
Lossless compression is a form of compression that only decreases file size a small amount but no data is lost during the process
Characters
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ASCII and Unicode are examples of character sets with extended ASCII allowing for 256 (2^8) possible characters
The Unicode character set allows for multiple languages and symbols to be represented, unlike ASCII
RAM
RAM is a volatile way in which we store memory. It holds currently used data, currently used instructions and currently used parts of the operating system
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