Fundamentals of Data Representation Flashcards
What is a natural number? (N)
A positive whole number used for counting and ordering.
Eg. 1,2,3,4
What is an integer? (Z)
A positive or negative whole number.
What is a relational number?(Q)
Any number that can be expressed as a fraction, with the numerator and denominator as whole numbers.
What is an irrational number?
A number that can’t be expressed as a fraction.
Eg. Root 2, pi
What is a real number?(R)
Any positive or negative value.
Used for measurements.
What is an ordinal number?
A number used to describe the numerical position of an object.
Eg. Second, fourth
What is a cardinal number?
A number used to describe a quantity.
Eg. One car, three dogs
What are the three number bases?
Base 2 - Binary - 0’s and 1’s
Base 10 -Denary - 0 -> 9
Base 16 - Hexadecimal - 0 -> 9 , A=10 -> F=15
What are the units of data in ascending order?
Bit x4
Nibble x2
Byte x1000
Kilobyte x1000
Megabyte x1000
Gigabyte x1000
Terabyte x1000
Petabyte x1000
What is a bit?
The smallest unit of data that can be processed by a computer.
What is the difference between a kilobyte and a kikibyte?
1 kilobyte = 1000 bytes
1 kikibyte - 1024 bytes
What is the difference between a signed and unsigned binary number?
Unsigned binary always has a positive value.
Signed binary could have either a positive or negative value.
How do you subtract 2 numbers using two’s complement?
1) Make the number being subtracted negative.
2) Do bitwise ADD on the two numbers.
How do you convert a positive number to a negative number?
1) Find the positive binary value
2) Flip the bits
3) Add binary value one
What is a parity bit?
A bit added to data to evaluate whether the data should be accepted or not.
What is majority voting?
A method of repeatedly sending the same bit multiple times, then the computer accepts the bit in majority.
What are the advantages of a parity bit?
Simple to implement
Low overhead
What are the disadvantages of parity bits?
Low reliability
No error correction
What are the advantages of majority voting
Reliable
Can detect and correct multiple-bit errors.
What are the disadvantages of majority voting
High overhead
Inefficient
What are check digits?
An additional digit at the end of a string of numbers designed to catch mistakes.
How do you calculate the check digit for ISBN-10?
Multiply by 10 then 9 then 8 ….
MOD 11
11 - ANS = check digit
How do you calculate the check digit for ISBN-13?
Multiply by 1 then 3 then 1 then 3…..
MOD 10
10 - ANS = check digit
What is a pixel?
The smallest element of an image.
What is a bitmap?
A map of where pixels should go.
What is the colour-depth?
The amount of bits needed to store all the colours for an image.
How do you calculate the number of colours?
2^colour-depth
What are true colour images?
24-but colour-depth images.
What is metadata?
Data about data.
What are examples of metadata?
Filename
Dimensions
Resolution
What is resolution?
The number of pixels in an image
width x height
What is the formula for the number of bits in an image?
resolution x colour-depth
What are vector images?
An image made up of objects and co-ordinates.
What are the advantages of vector images?
Never becomes pixelated
Smaller file size
What is a JPEG image?
A data format for lossy compressed photos.
What is a GIF image?
A data format for basic images that appear mainly on the internet. (8-bit)
What is a BMP image?
An uncompressed file format for high quality images.
What is a PNG image?
A lossless compressed file format that can handle transparent backgrounds.
What is a SVG image?
A web friendly vector file format.
What are raster graphics?
Using a bitmap to store images.
What is the difference between analogue and digital sound?
Analogue sound is infinite sound waves that travel through the air.
Digital sound is discrete values stored in binary form.
How does an Analogue to Digital Converter (ADC) work?
Records samples at regular intervals
Measure the amplitude of each sample
Assigns each sample a binary value
What is a MIDI?
A set of protocols that allow digital instruments to communicate.
Give examples on what a MIDI stores?
The note, how long the note is, the frequency of the not, how loud the note is. etc.
What are the advantages of a MIDI?
Small file size
High quality reproduction as no background noise etc.
Easy to edit
What is the sample rate?
How often you record the amplitude of a wave.
What is the sample resolution?
The number of graduations of amplitude that are represented. (Number of bits)
What is the formula for the sample size of a sound?
sample rate x sample resolution x length of recording (seconds)
What is the Nyquist theorem?
The frequency stored should be double the rate of the highest frequency for the best quality of sound.
What is compression?
The process of reducing a files size, allowing for faster transmission.
What is lossless compression?
Compression of a file, where the original data can be reproduced without any loss.
When is lossless compression used?
When the quality of the original file needs to be maintained.
What is run-length-encoding?
A method of lossless compression where repeated data is grouped together to reduce file size.
What is dictionary-based-encoding?
The lossless compression of text files buy storing common strings of characters.
What is a disadvantages of dictionary-based-encoding?
The dictionary may become longer than text itself.
What is lossy compression?
When unnecessary data is removed, where the original data can never be restored.
When is lossy compression used?
When quality isn’t necessary.
What can lossy compression not be used on?
Text files
Executable software
What is encryption?
The process of scrambling the contents of a file to render it unreadable by a third party.
What is plaintext?
Data that can be read by humans.
What is ciphertext?
Encrypted data.
What is decryption?
The process of deciphering encrypted data.
What is the Caesar cipher?
When the alphabet is offset by a fixed number to encrypt it.
How can the Caesar cipher be improved?
Polyalphabetic (use multiple alphabets)
Add keywords to the start of a message.
What are the disadvantages of the Caesar cipher?
Easy to crack as there are only 25 possible keys and certain letters are used more frequently than others.
What is the Vernam cipher?
It uses a one-time key pad, which is a unique key that is only used once to encrypt and decrypt a message.
How do you make a Vernam cipher?
Plaintext XOR one-time key pad
What are the advantages of the Vernam cipher?
If the key is completely random and only used once it is mathematically impossible to crack the code.
