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Data Representation
| Question | Answer |
|---|---|
| Binary | A number system that uses two digits, 0 and 1, base 2 |
| Bit | A binary digit; it can be 1 or 0 |
| Byte | A group of 8 bits |
| Word | A group of bytes |
| Denary number system | A number system that uses the digits 0 to 9, base 10 |
| Two’s complement | A system for representing negative numbers |
| Most significant bit | The left most bit. (A positive number always has 0 as the most significant bit. A negative number always has 1 as the most significant bit.) |
| Least significant bit | The right most bit. (An odd number always has 1 as the least significant bit. -1 is represented by a 1 in every bit, whatever the word size.) |
| Hexadecimal number system | A number system that uses the digits 0 to 9 and the letters A-F, base 16 |
| ASCII | ASCII is a character coding scheme which uses 7/8 bits and can therefore represent 128/256 different characters. |
| Unicode | Unicode is a character coding scheme which uses 16 bits to represent each character. (The extended ASCII codes are incorporated into Unicode representations) |
| Parity | Parity bits are added to bit patterns for error checking. Single parity bits can be used, or the Hamming Code, using several bits |
| Majority vote | This is when each bit is sent 3 times, and the most occurring bit is used to determine the correct one. However this is expensive as 3x the volume of data is transmitted |
| Hamming code | A system which can self-correct single errors using a few parity bits in a bit pattern. |
| Gray code | A binary code where each subsequent number only involves a single bit change. Gray code uses reflected binary code, ie bits 0-7 are reflected in bits 8-15 |
| Pixel | The smallest addressable area in an image |
| Bitmap | Created when the pixels of an image are mapped to positions in memory that store binary codes representing the colour of each pixel |
| Resolution of a VDU screen | A quantity expressed as the number of pixels per row by the number of pixels per column |
| Resolution of an image | A quantity expressed as the number of dots/pixels per inch or centimetre |
| Colour depth | The number of bits used to represent the colour of a single pixel in a bitmapped image |
| Vector graphic | Records geometric and other information about the objects that make up an image |
| Object | A component of a vector graphic, such as a line, a rectangle or a circle |
| Drawing list | The list of drawing commands that recreate a vector graphic |
| Property | Of a vector graphic object, describes things such as the size, direction, thickness, shading, font size or typeface |
| Data compression | Squeezes data into a smaller number of bytes than the data would occupy if uncompressed |
| Analogue data | Data that varies in a continuous manner |
| Digital data | Data that takes the form of discrete values |
| Analogue signal | An electrical signal that varies in a continuous manner |
| Digital signal | An electrical signal with voltage changes that are abrupt or in discrete steps |
| ADC | Analogue-to-digital converter; converts an analogue signal into an equivalent digital signal |
| DAC | Digital-to-analogue converter; converts a digital signal into an equivalent analogue signal |
| PCM | Pulse code modulation; a process for coding sample analogue signals by recording the height of each sample in a binary electrical equivalent. |
| PAM | Pulse amplitude modulation; a process that samples analogue signals at regular time intervals and produces electrical pulses of height proportional to the original signal’s amplitude at the instant of sampling |
| Quantisation noise | The difference between the original amplitude and its sampled wave |
| Nyquist’s theorem | Sample at a frequency at least twice the rate of the highest frequency in the sampled signal |
| MIDI | Musical information digital interface; a way of representing the sounds made by an instrument |
| Synthesise sound | Use digital means to generate audio signals resembling instrument sounds or the human voice |
Created by:
Masterniket
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