Data Rep Flashcards
What are natural numbers?
- A set of numbers containing all positive numbers and zero
- Used for counting
- Symbol = N
What are integer numbers
- Whole number
- Positive and Negative (Including 0)
- Symbol = Z
What are rational numbers?
- AKA Quotients
- Numbers that have a fractional part (one number over the other)
- Positive or Negative (0 is a rational number)
- Symbol = Q
What are irrational numbers?
- The number that cannot be written exactly as a fraction
- Symbol = N/A
What are real numbers?
- All possible real world quantities
- Used for measuring
- Includes:
- Irrational numbers
- Rational numbers
- Integers
- Natural numbers
- Symbol = R
What is ordinal numbers?
- Integers used for describing numerical positions
- Of objects in relation to one another
- Used in arrays where 0 is the 1st item in the list
What is base 10?
- Decimal / Denary
- Humans use to count (0-9)
- Represented through subscript ($27_{10}$)
What is base 2?
- Binary
- Only uses two characters for each digit
- 1 or 0 which can be represented through a high or low current
- Denoted through subscript 2 ($10110010_2$)
What is base 16?
- Hexadecimal
- Digits 0-9 then A-F
- make use of 16 different characters
- Denoted through subscript 16 ($7E_{16}$)
What is a bit?
- The fundamental unit of information
- Contains only one of two values 0 or 1
- Represented by high or low currents
- Can represent ****4 different values**** due to the 4 different permutations ($2^2$)
- Denoted with a lowercase b
What is a byte?
- A collection of 8 bits
- Can represent 256 different values $2^8$
- Half a byte is a nibble
- Denoted by a B
What are the different units starting from S and Kilo
What is the reason for the binary system?
- Where only 1 and 0 are used to represent values
- Can be represented by a high or low voltage
- Through transistors
What is the max value that binary can represent?
- Since there are 8 columns in the table
- It’s $2^8$ = 255
How do you convert binary numbers into denary?
How do you add binary numbers?
How do you add negative numbers?
What is the colums for twos compliment
How do you do float point binary?
How do you multiply binary?
What is analogue data?
Analogue
- Continuous
- No limits to the vales that data can take
- Takes any value and can change the frequency as required
What is digital data?
Digital
- Discrete
- Can only take particular values
- Takes a specified range of values and can only change value at specified intervals
How do you convert from digital to analogue?
Analogue to Digital
- ADC (Analogue to Digital Converter)
- Analogue signal → Digital bit pattern
- Sampling of analogue signal at regular intervals and records a value
- Used in temperature sensors and microphones
What is sampling?
- Records of data taken at regular intervals from an analogue signal
- Taken at a specific frequency in Hertz
- Determines sampling rate
- Number of samples per taken per second
how do you calculate the file size of a sound file?
****Duration of Sample(Sec) x Sampling Rate(Hz) x Sampling Resolution(bits) = File Size(bits)****
**Metadata also adds to file size but only add to equation if given**
What is the Nyquist Theorem?
Nyquist Theorem
- Sampling rate of a digital audio file must be at **least double the frequency of sound**
- If below this then it is **NOT**** and accurate representation of the sound
What are bitmap images?
- Bitmap graphics where each pixel is assigned a binary value
- has a resolution which is the amount of pixels in an image
- Pixel value represents the colour
What is colour depth?
- The number of bits assigned to each pixel
- The more bits you use the more information per pixel
- Meaning more colours can be represented
What is resolution?
The amounts of pixels per inch
What is colour depth
the number of bits needed to store each pixel (like colours)
How to calculate the file size for a bitmap image
size in pixels X the colour depth
What metadata?
- Extra information about the data
- Date created
- Dimensions
- Last modified
- Author
What are vector images / graphics
- Uses lists of information and maths to recreate data
What are the advantages of vector graphics?
- File size is small regardless of image scale
- Will always scale without loss of quality
- Easy manipulation of objects
- Good for logos / simple images
What is the disadvantages of vector images
- Cannot easily replicate an image with contionous areas of changing colour
- Individual pixels cannot be changed
What are the adantages of bitmapped images?
- Great form for storing full colour images taken on a phone
- Easy pixel manipulation
- Easy retouching/altering of images
What is the disavantages of bitmap images?
- Takes up more memory and storage space
- Distored when scaled beyond a certian point
- As images become pixelated th larger they become
What is MIDI
- A protocal
- Digital interface
- Standard set of connectors
- Allows for communication between a wide range of electronic musical intruments and computers
What is the difference between analogue and MIDI
- MIDI isnt a digital recording of a real sound
- Midi is a list of intructions
- To sythesise pre recorded samples of certain sounds
- Meaning the file size is smaller
What is lossy compression
- Reduces and removes data
- Origional cant be used
- Images and sound files
- JPEG,MP3
What is lossless compression?
- Uses redundent data removal
- Meaning a dictionary coding is created
- To reproduce the origonal file
- ZIP,PNG
What is dictionary encoding?
- Compression algorithm
- Uses an idex for repeated data
- Which is then used on the data which would be turned into a series of refrences to that data
What is RLE?
- Run length encoding
- Compresion algorithm
- Used on images where pixels are indexed
- Where repeating data is merged together
What is encryption?
- Used by encoding messages so it can only be read by the sender and the reader
- Requires a encryption and decryption key
What is Caesar cipher?
- Encryption algorithm
- Takes a letter and applies a shift in the alphebet depending on the key (number of shifts [5])
- Easy to crack with a brute force attack only 25 possibilities
What is vernam cipher?
- Uses a one time pad cipher
- Which must be longer or equal to plaintext message
- Key must be random
- Key should only be used once then destoryed
- Must be sent securly
How does vernam cipher work?
- Write out the ascii for the letter of the plaintext
- Then write out the ascii binary for the first letter of the one time pad
- Perform a XOR gate on the binary which would return a ascii character
- Repeat until whole message encrypted
- Reverse for decryption
What is ASCII?
- American Standard Code Information interchange
- Character encoding system
- 1 byte relates to one unquie character
- Only uses 7 bits as the last bit is used for error checking
- Same character sets needed to share text between computers
What is UNICODE?
- A larger characterset
- 16 bits long
- Allows for more symbol and accents
- Requries twice as much space
- Accounts for all langagues
What is error checking and what are the methods used?
- Allows for data transmission to be accurate
- Parity bits
- Majority voting
- Check Digits
- Checksums
How does parity bits work?
- Relies on odd and even bits
- First bit can be odd or even depending on the rest of the bits being odd or even
- Odd means more 1 than 0
- Even means more 0 than 1
What is the problem with parity bits
- If a 1 and a 0 is corrputed and changed
- There would be no change in the parity bit
- 1100 would be seen as correct when the data is meant to be 0011
How does majority voting work?
- Crude mothod of identifiying error in data by transmittting binary digits multiple times and then looking at the pattern recived
- If pattern doesnt match majority vodting it checks which bit occurs most frequently assuming its the correct bit
- Every bit has 3 repeated bits where if 110 is sent then 1 is the bit used
How does check digits work?
- A form of redundency
- Used for error checking on id numbers
- Which are used in an application to which can be input manually
- Check digit is the remainder data weight divided by the total data weight
How does checksums work?
- Mathematical algorithm applied to a block of data
- Data in the block is used to create the inital checksum which is then added transmitted along the original data
- Where each byte is turned into denary
- And the sum of those denary numbers is the checksum
What does fixed point binary accuracy depend on?
Depends on the number of bits avaliable
What does the accuracy of floating point binary depends on?
Depends on the size of the mantissa
How would you represent 0.1 in binary?
- Its impossible to get the number 0.1
- So we round to get the closest possible answer 0.9375
What is symmetric encryption
- Encryption where the both the user and the sender have the same key
- Vunerable to mad in the middle attacks
What is asymetric encryption
- Encryption where there are two different keys
- A public and private key
- Data can be intercepted but not decrpted without private file
Where is asymetric encryption used?
- HTTPS (SLL)
- SSH
- Bitcoin
- PGP
