Fundamentals of data representation Flashcards
What is a natural number
A whole number used in counting. In computing 0 is a natural number
What symbol represents a natural number
N
What is a rational number
Any value that can be expressed as a ratio or a fraction (Includes integer values)
What symbol represents a rational number
Q
What is an irrational number
A value that cannot be expressed as a fraction and has an endless series of non-repeating digits e.g Pi
What is an integer number
A whole number that could be positive or negative
What symbol represents integer numbers
Z
What is a real number
Any number that is natural, rational or irrational. Cannot be an imaginary number
What are ordinal numbers
Numbers used to count places in a list e.g 1st, 2nd
How does a parity bit work
If data is looking for odd parity they will look for an odd number of 1s and vice-versa for even parity
What are the drawbacks of using a parity bit
- It can only check for errors and not correct them
2. It may fail if there are an even amount of errors
What is majority voting
When the bits within a binary string are sent three times.
It will select the majority bit within the string once it has arrived
e.g 111000111 -> 111001110 - This will be corrected to the original
What is the advantage of majority voting over a parity bit
Not only checks for errors but corrects them as well due to the 2 additional bits being unlikely to change
What is a bitmap image
An image composed of pixels where each pixel is given a set binary value to represent a colour
What is a pixel
The smallest identifiable area of an image
How do you calculate image resolution
Number of pixels high * Number of pixels wide
What is image resolution
The number of pixels in an image
What is colour depth
The amount of bits assigned to each pixel
What happens when you have a high colour depth
More colours can be represented, increasing image quality
How do you work out the colour depth
2 to the power of the amount of bits
e.g 3 bits mean 2^3 so 8 colours can be represented
What is metadata
Data about data
Give examples of metadata
Filename
Date created
File type
How do you calculate minimum file size
Width in pixels * Height in pixels* Colour depth
What is digital data
All the processes carried out by a computer are digital Discrete data (Limited in detail)
What is analogue data
Inputs and outputs are analogue
Analogue data is continuous (infinite detail)
What is the amplitude in relation to sound waves
How loud the sound is
What is the frequency in relation to sound waves
The pitch of the sound
How do you convert analogue data to digital data
Analogue to digital converter - ADC
How do you convert digital data to analogue data
Digital to analogue converter - DAC
What is sampling
Taking points of an analogue sound wave and then converting this to digital
How can we improve the accuracy of the digital recording
Increase the amount of samples taken per second (Increase the sample rate)
What are CD’s usually sampled at
44,100 Hz
What are the results of a higher sample rate
More accurate at reflecting a true sound wave but file size increases
How many channels is mono, stereo and cinema channels
Mono - 1
Stereo - 2
Cinemas 5.1 - 6
What is sample resolution
The number of bits assigned to each sample
What happens as a result of low or high sample resolution
Low sample resolution - Results in a lower volume range
High sample resolution - Will result in a high file size
What is the sample resolution of a CD
16 bits
How do you calculate a recordings file size
File Size = Sample rate * Sample resolution * Length of recording
What is Nyquists Theorem
Sample rate must be twice the highest frequency
What is compression
Making a file smaller
What are the two types of compression
Lossless and Lossy
Give an example of a compression technique
RLE - Run Length Encoding
Dictionary based compression
How does dictionary based compression work
It identifies common patterns and creates a dictionary value based on this
What is a computationally secure cypher
A cypher that theoretically can be broken but in too long a time that it wouldn’t be useful
What is a digital certificate
A method of ensuring that an encrypted message is from a trusted source
What is SSL
Secure Socket Layer. Introduced to encourage business on the internet and was designed to tackle fraud
What are digital signatures used for
Used to identify the authenticity of the senders of emails
