Karteikarten
Data representation
Karten in diesem Stapel (61)
- 1name all the prefixes for bits and bytes in orderbit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte
- 2how many bits are in a nibble?4 bits (half a byte)
- 3how many bits are in one byte8 bits
- 4how many bytes are in a kilobyte1000 bytes
- 5how many kilobytes are in a mega byte1000 kilobytes (1000x1000 bytes)
- 6how many Mega bytes are in a giga byte1000 MB
- 7how many giga bytes are in a terabyte1000GB
- 8the file size of one character of text? the file size of a full page of text? the file size of a small digital photo in colour? file size of Music CD Capacity? DVD Capacity hard disk capacity file size?1) 1 byte
2) 30 kB
3) 3 MB
4) 650 MB
5) 4.5 MB
6) 1 TB - 9why do computers use binarythis is because binary is the language in which the computer understands and processes/stores information
- 10what is the most and significant bitthe most significant bit is the bit with the largest value (this is the bit that is furthest to the left) the least significant bit is the bit with the smallest value (this is the bit that is furthest to the right)
- 11in hex how are numbers represented?0-9 are digits but from 10-15 uses letters A-F
- 12how do you covert a hexadecimal number to decimal e.g. convert 2A into decimalyou multiply the left-hand digit by 16 and then add the units
(2x16) + 10 = 42 - 13how do convert a number from decimal to hex? e.g convert 18 to hexadecimaldivide the left-hand digit by 16 and remainder is the units
18/16 = 1 remainder 2
= 12 - 14why do people use hex rather than binary?it is much simpler to remember a hex value than a binary value.
it is quicker to write or type since a hex digit only taxes up one digit rather than 4 bits
people are less likely to make an error with fewer digits
it is easy to convert between hex and binary - 15what are the rules of binary addition1) 0 + 0 = 0
2) 0 + 1 = 1
3) 1 + 1 = 0 carry 1
4) 1 + 1 + 1 = 1 carry 1 - 16what problem can occur when you add two binary value that are too big?an overflow error
- 17what is an overflow error?when the result of an edition is too large for the number of buts the computer works with there will be an overflow error
- 18what solves overflow errors?logical binary shift operations
- 19true or false: vacant bit spaces in logical binary shifts are filled with zerostrue
- 20what are the effects of shifts?logical shifts can very quickly multiple or divide a binary number by a factor of 2.
left shifts multiply, right shifts divide
a loss of accuracy can occur if 1 bits are removed - 21how many characters are on a standard keyboard? how many bits would be required to represent this number of combinationthere are 98 unique characters that are available on a keyboard, 7 bits give 128 different combinations which can represent 128 different characters
- 22what is a character set? what are two examples of a character set?a character set is a set of letters, symbols and digits that can be represented by a computer.
ASCII and Unicode (and extended ASCII) - 23what does ASCII encode?it encodes the English alphabet - it encodes 128 characters into 7 bit binary codes
- 24what does 8 bit ASCII allowit allows for other characters to be introduced for example emoticons and é
- 25what was the problem with 7 bit and 8 bit ASCII?it didn't for characters for different languages alphabet to be included as to didn't have enough different combinations available
- 26what was introduced to combat the limitations of 7 and 8 bit ASCII?Unicode (use 16 bits - 65 536 combinations)
- 27what are all the different bitmap file formats?BMP, JPG, GIF, PNG, TIFF
- 28what is a pixel?shorter for Picture elements, a pixel is the smallest identifiable area of an image
- 29what is image resolution?resolution is the concentration of pixels within an specific area (width and height) in PPI (pixels per inch)
- 30what is the colour (bit depth)each pixel can represent a finite number of colours
the colour (bit) depth is number of combinations and therefore the number of colours that can be represented - 31what is the effect of a higher colour (bit) depth?a higher bit depth gives a greater range of colour and a better quality of image
- 32what is the effect of varying the colour depth of an image?changing the colour depth of an image will effect the number of colours it can display
- 33how does the number of colours affect the file size?An increase in the number of colours that are used in an image (bit / colour depth) will increase the file size
- 34how does the size of an Image affect file size?size has two meanings:
an increase in the number of pixels in the image, will increase the file size
if an images physical size is increased by making each pixel larger then there is no change in the file size. - 35how are colour values of individual pixels expressed?colour values of individual pixels are expressed in software as decimal RGB values and in hexadecimal. RGB values range between 0-255
- 36how do you calculate the image size in bitsWIDTH X HEIGHT X COLOUR DEPTH
- 37how do you calculate the size of an image in bytes(WIDTH X HEIGHT X COLOUR DEPTH) / 8
- 38what is metadata and what does it include?Metadata is data about data and includes the following information: Colour depth in bits per pixel, resolution, date created and author
- 39describe analogue sound signalsanalogue sound signals are continuous
- 40describe digital signalsdigital signals are discrete which means the sound wave is sampled at regular intervals
- 41how is sound digitised?sound is digitised by repeatedly measuring and recording the sound wave
- 42why are sounds converted in digital form?this is in order for the sound to be stored and processed by a computer
- 43what is analogue to digital convertors (ADC) used forAnalogue to digital convertors are used to convert inputs to digital signals
- 44what are digital to audio convertors (DAC) used for?to convert digital signals to outputs
- 45what is sound samplingsound sampling is a measurement of amplitude of a sound wave at a give time
- 46how is sound sampled and what does the sample resolution determinesound is sampled using a sample resolution (bit depth) and a sampling rate.
the sample resolution determines how closely the wave is sampled on the y-axis - 47define the term sample ratethe sample rate is the number of samples taken per second and is measured in Hz (1Hz = 1 sample per second)
- 48what effect the sampling rate have?the sample rate per second (frequency) affects the level of detail in the digital representation
the greater the frequency, the greater the accuracy and file size - 49define sample resolution and the effect of more bits used per samplethe number of bits used to record each measurement (sample resolution / bit depth)
more bits used per sample enables the height of the wave to be more accurately measured but increases file size - 50what's the formula to calculate sound file sizes?File size (in bits) = sampling rate x resolution x duration
File size (in bytes) = (sampling rate x resolution x duration) / 8 - 51the recording quality of digitised sound improves how?the more frequently we sample the sound, the more accurately we record the wave height
- 52what does increasing the sampling rate (frequency) meanit means recording more data points, increasing the bit rate improves the accuracy of each data point
- 53what happens to the size of the sound file if the frequency and bit-rate are increased?the file size increases.
- 54why is compression usedCompression is often used for files and data that are sent via the internet
Download times are reduced
Data allowances go further
It is possible to transmit music and data streams as fast as they are playing - 55what is lossless compression?lossless compression reduces the file size when compressed but doesn't lose any information - no data is lost so when the file is decompressed it will go back to its original format
- 56when would you use lossless compressionsending legal documents, data, books, high quality images etc
- 57what is lossy compression?Lossy compression permanently loses some data when reducing file size
You'd use lossy compression when you'd use it in image files and sound files
Lossy compression results in small mistakes known as 'digital artifacts' appearing in images as video where data has be lost - 58what are the benefits to using compressionSmaller files = fewer packets = faster transmission time. Quicker to complete transmission . Reduces traffic over the internet . Reduces download times of video, sound (including speech used for VOIP systems) and image files. Streaming is possible at the rate it is played
Images inside web pages appear faster
Reduces space on discs or servers - 59using run length coding how is 1111000000000000 represented4 1 12 0
- 60when is lossless text compression usedit encodes each pattern of repeated patterns (words, punctuation, spaces) in the original text in a dictionary
- 61how are Huffman trees usedhuffman coding analyses the frequency with which characters in a body of text are used. characters are then placed in a binary tree structure where most frequent occurring characters are placed nearest the top of the tree
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- GCSE Computing (Data Represntation) Karteikarten am Data representation, erstellt von lucy hay am 17/10/2022.
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- lucy hay
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