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Chapter 26 - Data Coding Systems - Definitions
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- 1Character CodeA binary representation of a particular letter, number or special character.
- 2ASCII - American Standard Code for Information InterchangeA standard binary coding system for all of the keyboard characters, including the numbers and special functions. It is a 7 bit code but can be extended to 8 bits to double the number of characters it can represent.
- 3UnicodeA standard binary coding system that has superseded ASCII. It was created because ASCII simply did not have enough space to represent all of the possible characters numbers and symbols (128), whereas Unicode uses 16 bits so can represent 65536 different characters.
- 4Parity bitA method of checking binary codes by counting the number of 1s and 0s in the code. The parity bit is the extra but added to the end of the binary code to make the number of 1s be even (even parity) or odd (odd parity). The computer knows what kind of parity it is looking for.
- 5Majority VotingA method of checking for errors by producing the same data several times and checking it is the same each time. The computer will take the most common form of each bit so if a bit is send twice as a 1 and once as a 0 the computer will assume that it was a 1.
- 6Check DigitA digit added to the end of binary data to check the data is accurate. The check digit is created by taking the original number itself and using it in some way to create a single digit. The computer at the other end knows how to create this digit and does the same process, if its different then something is corrupt.
- 7Bit mapped graphicAn image made up of individual pixels in a grid pattern, the number of these pixels defines the resolution of the image. Each pixel has its own binary code defining its colour, in a simple 1 bit graphic it can be either white (1) or black (0).
- 8PixelAn individual picture element, these are tiny elements of illumination that make up a picture in a bit mapped graphic. A typical monitor might have a grid of 1366 x 768 pixels, this is the resolution.
- 9ResolutionThe number of pixels in a display or an image. it is calculated using the width x height or pixels per inch.
- 10Colour DepthThe number of bits or Bytes allocated to represent the colour of each pixel in a bit-mapped graphic. In a black and white image each pixel is given 1 bit - 1 for white and 0 for black.
- 11Vector GraphicAn image made up of objects and coordinates, the image is made up by knowing the start, size, shape and colour of an area and the picture is created at the end. So if I created a vector graphic of a square you wouldn't need to store the entire area taking up loads of data, all you would need are the descriptions.
- 12Analogue SoundSound sampled as an analogue wave with amplitude, frequency and infinite variability. In order to sample one you need to take multiple readings at fixed intervals and each of these are given a binary value. When it is sampled it is stored digitally. This is done in ADCs
- 13Digital SoundA digital signal refers to an electrical signal that is converted into a pattern of bits. Unlike an analogue signal, which is a continuous signal that contains time-varying quantities, a digital signal has a discrete value at each sampling point. A computer can only read in digital so when an analogue signal is sampled it is stored digitally.
- 14CompressionThe process of reducing the number of bits required to store data. This is needed so large files can be stored and sent as smaller files as to not take up too much memory space or bandwidth when downloading.
- 15Run-Length EncodingA method of compressing data by eliminating repeated data.
- 16Dictionary-Based EncodingA method of compressing text files - it works by changing common words into symbols that can be read as the words by the computer at the other end, this means that none of the data from the text file is lost.
- 17Lossy CompressionThis is a way of compressing data by losing some of the accuracy of the data and in turn reducing the file size. This is fine with things like images or video and audio because a high deal of accuracy is not essential, whereas this would not be appropriate for text files where all the data is essential.
- 18Lossless compressionThis is a form of data compression where none of the accuracy of the data is lost. This is essential for things like text files where all of the original data is needed. You can also use this for images because you can group pixels of the same colour together.
Información
- Descripción
- The Definitions are the first sentence of each card with a more detailed description coming later.
- Creado por
- George Bettley
- Visitas
- 18
- Valoración