Data representation Flashcards
What is a bit?
A single 0 or 1
What is a byte
8 bits
What is a nibble
4 bits
How many bytes in a kilobyte
1000
What is the most significant bit?
The bit with the largest value (128)
What is the least significant bit?
The bit with the smallest value.
How can we convert 8 bit binary to hex?
Split the binary into two four bit binary, and convert each one into the relevant hex value.
Vice versa for hex to binary
Why is hexadecimal used?
Simpler to remember than binary
Quicker to write or type as it uses 1 digit rather than 4 bits
People less likely to make an error
Easier to convert into binary
What is an overflow error when adding binary
When the result of an addition is too large for the number of bits the computer works with
What is a character set?
A set of letters, symbols and digits that can be represented by a computer
What does ASCII stand for?
American Standard Code for Internet Interchange
What does concatenate mean?
Two strings that are joined together.
How many bits does ASCII use?
7 bits, which means that 128 characters can be stored
Why is Unicode also used as a character set?
Unicode is used as it can store more characters from many different languages
It can also store emojis
What is pixel an abbreviation of?
Picture element
What is a pixel?
The smallest identifiable element of an image
What is resolution?
Resolution is the concentration of pixels within a specific area
72 PPI - 17 pixels per inch
How can we work out the number of different colours that are available using the colour depth?
2^bit depth = number of colours
A colour depth of 4 means 2^4 colours, which is 16
How can we work out the file size of an image?
Resolution x bits per pixel
What is metadata?
Other information about the data
Colour depth
Resolution
Date created
Author
What is ADC
Analogue to Digital Converter
What is DAC
Digital to Analogue Converter
What is the sound sample?
A measure of amplitude of a soundwave at a given time
What is sample resolution?
The bit-depth (how clear the sound is)
What is the sample rate?
The number of samples taken per second
How can we calculate the file size for a sound file?
File size = sample rate x resolution x duration
What is lossy compression?
Removes sounds we can’t hear or that least affects the perceived playback quality
What is lossless compression?
Reduces the file size without removing any information
What is compression?
The name given to algorithms that reduce file sizes
What are examples of lossy compression file types?
JPG
GIF
MP3
What are examples of lossless compression file types?
TIFF
PNG
What is RLE?
Run length encoding uses frequency / data pairs to encode each run length of the same coloured pixel
What is Huffman coding?
Huffman coding counts the frequency of each character in a Huffman tree
What are the advantages of compression?
Download times reduced
Data allowances go further
Possible to transmit video and music as fast as they are being played
Why are smaller files sent faster?
Fewer packets which means they are transmitted faster
What is buffering?
When the download speed is slower than the playback speed
