2.1 Fundamentals of data representation Flashcards
Define natural number
A positive whole number including zero
Define integer
Any whole positive or negative number including zero
Define rational number
Any number that can be expressed as a fraction or ratio of integers
Define irrational number
A number that cannot be represented as a fraction or ratio as the decimal form will contain infinite repeating values
Define real number
Any positive of negative number with or without a fractional part
Define ordinal number
A number used to identify position relative to other numbers
Define cardinal number
A number that identifies the size of something
Define well-ordered set
A group of related numbers with a defined order
Define number base
The number of digits available within a particular number system
Define bit
A single binary digit from a binary number - either a zero or a one
Define byte
A group of bits, typically eight, used to represent a single character
Define unit
The grouping together of bits or bytes to form larger blocks of measurement
Define unsigned binary
Binary that represents positive numbers only
What is two’s complement?
A method of working with signed binary values
Define fixed point
Where the position of the decimal / binary point is fixed within a number
Define floating point
Where the position of the decimal / binary point can move within a number
Compare floating point and fixed point representation
- Floating point gives a wider range of numbers possible to produce from the same number of bits
- It can be faster to process fixed point values as processing the decimal point can be similar to integers
- The absolute error will be constant with fixed point whereas with floating point this could vary
Define signed binary
Binary with a positive or negative sign
Define overflow
When a number is too large to be represented within the number of bits allocated
Define underflow
When a number is too small to be represented within the number of bits allocated
Define precision
How accurate a number is
Define normalisation
A process for adjusting numbers onto a common scale
Define mantissa
The significatn digits that make up a number
Define exponent
The power part of a number indicating how far a binary point should be shifted left or right
Define character code
A binary representation of a particular letter, number, or special character
What is ASCII?
A standard binary coding system used for characters and numbers
Why was Unicode needed?
- 256 characters are not enough to represent all of the possible characters, number, and symbols
- It was initially developed in English and therefore did not represent all of the other languages and scripts used in the world
- Widespread use of the web made an international encoding system more important
How do parity bits function?
Using a parity bit is a method of checking binary codes by counting the number of 0s and 1s in the code. Either even or odd parity will be agreed upon before communication begins. With each piece of data sent, the number of 1s in the data will be counted. If even parity is agreed upon, for example, and the number of 1s in the data is odd, a 1 will be added as a parity bit. Conversely, if there is already an even number of 1s, a 0 will be added as a parity bit. If the recieved parity matches the agreed parity, the recieved message is assumed to be correct
How does majority voting work?
Majority voting is a method of checking for errors by producing the same data several times and seeing if the data is the same each time. When data is being sent, it will be sent multiple separate times, and the most common digit in each position will be assumed to be the correct one
How do check digits work?
A check digit is a digit added to the end of binary data to ensure that it is accurate. The check digit is generated by performing some sort of function on the data sent that gives a unique digit. This value is then also calculated by the reciever once the data has been recieved. If the recieved check digit matches the calculated one, then the data is assumed to be correct
Define pixel
An individual picture element
Define resolution
width x height or pixels per inch
What is a bit-mapped graphic?
An image made up of individual pixels
Define colour depth
The number of bits or bytes allocated to represent the colour of a pixel in a bit-mapped graphic
Define vector graphic
An image made up of objects and coordinates
What is the difference between analogue and digital data?
Analogue data is infinitely variable and can often be represented in the form of a wave, whereas digital data is often represented as discrete values
What data can be controlled in MIDI sound?
- When to play a note
- When to stop playing the note
- Timing a note to play with other notes or sounds
- Timing a note to play with other MIDI-enabled devices
- What pitch a note is
- How loud to play anote
- What effect to use when playing a note
What are the advantages of MIDI?
- File sizes tend to be much smaller meaning they require less memory and can be loaded faster, which is especially useful when used over the Internet
- MIDI files are completely editable as individual instruments can be modified
- MIDI supports a wide range of instruments and options for customisation
- MIDI can produce authentic and high-quality representations of an instrument
What is Nyquist’s theorem?
To faithfully recreate an analogue signal, you should sample at at least twice the highest frequency of the signal
Define sample rate
The number of samples that will be taken per second
How does analogue sound sampling work?
- A series of samples of the amplitude of the wave are recorded
- The original sound can then be reproduced by connecting these amplitudes to give a reconstruction of the original wave
- With a greater sample rate, the stored sound will be more accurate to the original sound wave
Define compression
The process of reducing the number of bits required to represent data
What are the 2 types of compression?
- Lossy: there will be some degradation / loss of the data in compression
- Lossless: the compressed file is accurate to how it was before compression
What is run-length encoding?
A method of compressing data by eliminating repeated data - this is a type of lossless compression
What is dictionary-based encoding?
A method of compressing text files
Define encryption
The process of turning plaintext into scrambled ciphertext which can only be understood if it is decrypted
Define decryption
The process of deciphering encrypted data or messages
What is plaintext?
Data in human-readable form
What is ciphertext?
Data tat has been encrypted
What is a caesar cipher?
A substitution cipher where one character of plaintext is substituted for another, which becomes the ciphertext
What is a vernam cipher?
A method of encryption that uses a one-time pad (key) to create ciphertext that is mathematically impossible to decrypt without the key
What is a transposition cipher?
A method of encryption where the characters are rearranged to form an anagram
Define key
In cryptography it is the data that is used to encrypt an decrypt the data
What is a substitution cipher?
A method of encryption where one character is substituted for another to create ciphertext
What is frequency analysis?
The study in cryptography of how often different letters or phrases are used
What is a railfence cipher?
A type of transposition cipher that encodes the message by splitting it over rows
What is a route cipher?
A type of transposition cipher that encodes the message by placing it into a grid
What is a one-time pad?
A key that is used only once to encrypt and decrypt a message and is then discarded
Define computational security
A concept of how secure data encryption is
Define computational hardness
The degree of difficulty in cracking a cipher
