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[OBSELETE] AQA - A Level CS > Data Rep > Flashcards

Data Rep Flashcards

1
Q

What are natural numbers?

A
  • A set of numbers containing all positive numbers and zero
  • Used for counting
  • Symbol = N
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2
Q

What are integer numbers

A
  • Whole number
  • Positive and Negative (Including 0)
  • Symbol = Z
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3
Q

What are rational numbers?

A
  • AKA Quotients
  • Numbers that have a fractional part (one number over the other)
  • Positive or Negative (0 is a rational number)
  • Symbol = Q
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4
Q

What are irrational numbers?

A
  • The number that cannot be written exactly as a fraction
  • Symbol = N/A
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5
Q

What are real numbers?

A
  • All possible real world quantities
  • Used for measuring
  • Includes:
    • Irrational numbers
    • Rational numbers
    • Integers
    • Natural numbers
  • Symbol = R
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6
Q

What is ordinal numbers?

A
  • 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
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7
Q

What is base 10?

A
  • Decimal / Denary
  • Humans use to count (0-9)
  • Represented through subscript ($27_{10}$)
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8
Q

What is base 2?

A
  • 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 ($10110010_2$)
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9
Q

What is base 16?

A
  • Hexadecimal
  • Digits 0-9 then A-F
  • make use of 16 different characters
  • Denoted through subscript 16 ($7E_{16}$)
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10
Q

What is a bit?

A
  • 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
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11
Q

What is a byte?

A
  • A collection of 8 bits
  • Can represent 256 different values $2^8$
  • Half a byte is a nibble
  • Denoted by a B
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12
Q

What are the different units starting from S and Kilo

A
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13
Q

What is the reason for the binary system?

A
  • Where only 1 and 0 are used to represent values
  • Can be represented by a high or low voltage
    • Through transistors
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14
Q

What is the max value that binary can represent?

A
  • Since there are 8 columns in the table
  • It’s $2^8$ = 255
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15
Q

How do you convert binary numbers into denary?

A
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16
Q

How do you add binary numbers?

A
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17
Q

How do you add negative numbers?

A
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18
Q

What is the colums for twos compliment

A
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19
Q

How do you do float point binary?

A
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20
Q

How do you multiply binary?

A
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21
Q

What is analogue data?

A

Analogue

  • Continuous
  • No limits to the vales that data can take
  • Takes any value and can change the frequency as required
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22
Q

What is digital data?

A

Digital

  • Discrete
  • Can only take particular values
  • Takes a specified range of values and can only change value at specified intervals
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23
Q

How do you convert from digital to analogue?

A

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
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24
Q

What is sampling?

A
  • 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
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25
Q

how do you calculate the file size of a sound file?

A

****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**

26
Q

What is the Nyquist Theorem?

A

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
27
Q

What are bitmap images?

A
  • 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
28
Q

What is colour depth?

A
  • The number of bits assigned to each pixel
  • The more bits you use the more information per pixel
  • Meaning more colours can be represented
29
Q

What is resolution?

A

The amounts of pixels per inch

30
Q

What is colour depth

A

the number of bits needed to store each pixel (like colours)

31
Q

How to calculate the file size for a bitmap image

A

size in pixels X the colour depth

32
Q

What metadata?

A
  • Extra information about the data
  • Date created
  • Dimensions
  • Last modified
  • Author
33
Q

What are vector images / graphics

A
  • Uses lists of information and maths to recreate data
34
Q

What are the advantages of vector graphics?

A
  • File size is small regardless of image scale
  • Will always scale without loss of quality
  • Easy manipulation of objects
  • Good for logos / simple images
35
Q

What is the disadvantages of vector images

A
  • Cannot easily replicate an image with contionous areas of changing colour
  • Individual pixels cannot be changed
36
Q

What are the adantages of bitmapped images?

A
  • Great form for storing full colour images taken on a phone
  • Easy pixel manipulation
  • Easy retouching/altering of images
37
Q

What is the disavantages of bitmap images?

A
  • Takes up more memory and storage space
  • Distored when scaled beyond a certian point
  • As images become pixelated th larger they become
38
Q

What is MIDI

A
  • A protocal
  • Digital interface
  • Standard set of connectors
  • Allows for communication between a wide range of electronic musical intruments and computers
39
Q

What is the difference between analogue and MIDI

A
  • 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
40
Q

What is lossy compression

A
  • Reduces and removes data
  • Origional cant be used
  • Images and sound files
  • JPEG,MP3
41
Q

What is lossless compression?

A
  • Uses redundent data removal
  • Meaning a dictionary coding is created
  • To reproduce the origonal file
  • ZIP,PNG
42
Q

What is dictionary encoding?

A
  • 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
43
Q

What is RLE?

A
  • Run length encoding
  • Compresion algorithm
  • Used on images where pixels are indexed
  • Where repeating data is merged together
44
Q

What is encryption?

A
  • Used by encoding messages so it can only be read by the sender and the reader
  • Requires a encryption and decryption key
45
Q

What is Caesar cipher?

A
  • 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
46
Q

What is vernam cipher?

A
  • 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
47
Q

How does vernam cipher work?

A
  1. Write out the ascii for the letter of the plaintext
  2. Then write out the ascii binary for the first letter of the one time pad
  3. Perform a XOR gate on the binary which would return a ascii character
  4. Repeat until whole message encrypted
  5. Reverse for decryption
48
Q

What is ASCII?

A
  • 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
49
Q

What is UNICODE?

A
  • A larger characterset
  • 16 bits long
  • Allows for more symbol and accents
  • Requries twice as much space
  • Accounts for all langagues
50
Q

What is error checking and what are the methods used?

A
  • Allows for data transmission to be accurate
  • Parity bits
  • Majority voting
  • Check Digits
  • Checksums
51
Q

How does parity bits work?

A
  • 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
52
Q

What is the problem with parity bits

A
  • 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
53
Q

How does majority voting work?

A
  • 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
54
Q

How does check digits work?

A
  • 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
55
Q

How does checksums work?

A
  • 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
56
Q

What does fixed point binary accuracy depend on?

A

Depends on the number of bits avaliable

57
Q

What does the accuracy of floating point binary depends on?

A

Depends on the size of the mantissa

58
Q

How would you represent 0.1 in binary?

A
  • Its impossible to get the number 0.1
  • So we round to get the closest possible answer 0.9375
59
Q

What is symmetric encryption

A
  • Encryption where the both the user and the sender have the same key
  • Vunerable to mad in the middle attacks
60
Q

What is asymetric encryption

A
  • Encryption where there are two different keys
  • A public and private key
  • Data can be intercepted but not decrpted without private file
61
Q

Where is asymetric encryption used?

A
  • HTTPS (SLL)
  • SSH
  • Bitcoin
  • PGP

[OBSELETE] AQA - A Level CS (13 decks)

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