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A-LEVEL Computing - OW > Topic 5 - Data Representation - Complete > Flashcards

Topic 5 - Data Representation - Complete Flashcards

1
Q

Define natural numbers? (N)

A

WHOLE POSITIVE NUMBERS
Is a whole number that is used in counting
N = {0,1,2,3,4,5}

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2
Q

Define integer numbers? (Z)

A

Includes the natural numbers and their negatives. Can’t be a fraction
Z = {-2,-1,0,1,2}

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3
Q

Define rational numbers? (Q)

A

Can be written as a simple fraction or ratio

Q = {7/2, 8/1, 1/2}

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4
Q

Define irrational numbers? (Q’ or no symbol)

A

Cannot be written as a fraction or ratio
(not all square roots are irrational e.g. √4 = 2)
Q’ = {√2, √3, π, √99}

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5
Q

Define real numbers? (R)

A

Used for measurement

Includes whole numbers, integers, rational numbers, irrational numbers, positive or negative or 0.

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6
Q

Define ordinal numbers?

A

Used to describe the position of an object in an ordered list
a = 1st
b = 2nd
c = 3rd

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7
Q

Define base 10?

A

Is decimal

{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

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8
Q

Define base 2?

A

Is binary

{0,1}

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9
Q

Define base 16?

A

Is hexadecimal

{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F}

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10
Q

What is the number arrangement for converting binary to decimal?

A

128, 64, 32, 16, 8, 4, 2, 1

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11
Q

Define the 5 things:

  • Binary code
  • Bit
  • Byte
  • nibble
  • Kibibyte
A
  • Based on a number system that uses 0 & 1.
  • A single binary digit that can have values of 0 & 1.
  • A group of 8 bits. Max decimal is can store is 255.
  • A group of 4 bits or half a byte.
  • Unit used for digital information, 1 kibibyte = 1024 bytes
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12
Q

What are the binary powers for units:

  • Kibibyte
  • Mebibyte
  • Gibibyte
  • Tebibyte
A
  • Kibibyte = 2^10
  • Mebibyte = 2^20
  • Gibibyte = 2^30
  • Tebibyte = 2^40
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13
Q

What are the decimal powers for units:

  • Kilobyte
  • Megabyte
  • Gigabyte
  • Terabyte
A
  • Kilobyte = 10^3
  • Megabyte = 10^6
  • Gigabyte = 10^9
  • Terabyte = 10^12
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14
Q

Define signed binary?

A

Numbers which indicate they are positive or negative

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15
Q

Define unsigned binary?

A

Numbers which don’t indicate if they are positive or negative - can be used to store larger numbers.

Min value = 0 and max value = 2^n-1

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16
Q

What are the 4 rules of binary addition?

A

0+0=0
0+1=1
1+1=0,1
1+1+1=1,1

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17
Q

Define signed binary using two’s complement?

A

The most significant bit will indicate 1 for a negative number and 0 for positive.

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18
Q

What are the steps for two’s complement?

A

Flip the digits

Add 1

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19
Q

Define fixed point binary?

A

Is used to represent a fractional part of a number, where the binary point is in a fixed location.

128, 64, 32, 16, 8, 4, 2, 1. 1/2, 1/4, 1/8, 1/16, 1/32

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20
Q

Define normalised floating point?

A

Is where the binary point position is fixed in a standard form position and the exponent can float to reflect different values of that number.

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21
Q

Define the mantissa?

A

Is the part of the floating-point number that includes the significant digits within a number.

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22
Q

Define the exponent?

A

Is the number that the mantissa is shifted right or left by.

Is the power that the number within the mantissa is raised.

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23
Q

Which order is the mantissa & exponent?

A

Mantissa & exponent

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24
Q

Define underflow?

A

Occurs where the required value is too small to be stored using the number of bits available.

25
Q

Define overflow?

A

Occurs where the required value is too large to be stored using the number of bits available.

26
Q

Define ASCII?

A

Is a 7-bit character set which offers 128 different characters. Each character has an ASCII value for its upper and lower case.

American Standard Code for Information Interchange

27
Q

Define Unicode?

A

Is a 16-bit character set which offers 65,536 different characters. It includes the characters for any writing system.

28
Q

Define parity bit checking?

A

Carried out on data that is transmitted.
Parity is a simple method of ensuring the integrity of the data that has been received.
Parity checking is only able to detect an odd number of errors and can’t correct them.

29
Q

Define even parity?

A

Is where the number of 1’s is counted and if the number of 1’s is odd then the parity bit is set to 1.

30
Q

Define odd parity?

A

Is where the number of 1’s is counted and if the number of 1’s is even then the parity bit is set to 1.

31
Q

Define majority voting?

A

Can detect and correct errors.

Each bit is sent 3 times and checked each time. If a digit is different from the majority of the other digits there is an error. It then corrects this.

32
Q

Define checksum?

A

Error detection method
Number of bits transmitted in a message is counted, this checksum is compared with a count of the data received to check the integrity of the data transmission.

33
Q

Define check digits?

A

Is added to binary data to check that the data is accurate.

Used by stores to check that the bar code printed on an item of shopping has been correctly entered into the computer.

34
Q

Define a bit pattern?

A

Is an arrangement of binary digits in a sequence.

They can be used to represent text, images, video and sound.

35
Q

Define analogue?

A

Is continuous
Infinite amount of binary
Sound into a microphone into a computer is analogue

36
Q

Define digital?

A

Is discrete
Binary which computers understand
A sound wave stored as a series of numbers in a computer.

37
Q

Define ADC?

A

Analogue to digital converter
Receives signals input via an analogue sensor in the form of voltage waveforms which are converted into a digital format so they can be read into a computer.

38
Q

Define DAC?

A

Digital to analogue converter
Converts a discrete digital signal into a continuously varying analogue signal
Sound coming out of speakers

39
Q

Define colour depth?

A

Is the number of bits used for each pixel, where 1-bit is 2 colours (black and white), 8-bits is 256 colours.
2^n

40
Q

Define the equation for image resolution?

A

Pixel dimensions height * width

41
Q

Define display resolution?

A

is the number of dots per inch(DPI)

More dots per inch give a better image resolution

42
Q

Define metadata?

A 
'Data about data'
Provides details of properties: 
- image dimensions 
- colour depth 
- image name & size.
43
Q

Equation for storage of image?

A

width * height * colour depth

44
Q

Define vector graphics?

A

Are produced in graphics packages and are created using a series of objects and their coordinates.

45
Q

2 differences between bitmapped and vector graphics?

A

Bitmapped used for digital photography
Vector used for engineering drawings

Bitmap images stored as pixels
Vector images stored as objects

46
Q

Define sampling rate?

A

Is the number of samples taken per second from the analogue input to create a digital signal

47
Q

Define Nyquist’s theorem?

A

The sound must be sampled at twice the highest analogue frequency to create an accurate representation of the original waveform.

48
Q

Define sampling resolution?

A

Is the number of bits used to store each sample.

49
Q

Define MIDI?

A

Is a protocol that is used to synthesise musical instruments. Sound can be edited, overlays made,

Musical instrument digital interface

50
Q

Define data compression?

A

reduces the file size to allow download times and file storage requirements to be reduced.

51
Q

Define lossless compression?

A

Allow the original data to be perfectly reconstructed, resulting in no loss of data.

52
Q

Define lossy compression?

A

Result in a loss of data, so the original data can’t be reconstructed.

53
Q

One advantage of lossless compression?

A

The file can be compressed for download or to load on a website but can be recreated exactly

54
Q

One advantage of lossy compression?

A

Unnecessary data can be reduced to compress files, overall output quality is acceptable.

55
Q

Define run-length encoding?

A

Is a form of lossless compression where a sequence that contains a repeated value of data is replaced by a single value of that data with a count of the number of times it occurred.

56
Q

Define encryption?

A

Is used to make stored data more secure from hackers, by making it unreadable to people with unauthorised access. to the key to decrypt or decode it.

57
Q

Define Caesar cipher?

A

Is a simple substitution cipher.
Using each plaintext letter to be replaced with another letter. The letters could be shifted by a certain amount.
ABCDEF (Shift by 3)
XYZABC

58
Q

Define Vernam cipher?

A 
One-time pad cipher.
Is a digital data stream cipher that is combined with the same length random stream of data to create a ciphertext, based on the boolean exclusive OR function.
(A)  (B)  (A XOR B)
 0    0                0
 1     0                1
 0     1                1
 1      1                0
59
Q

Define computational security?

A

Indicate the effectiveness of a cipher.
Vernam is considered 100% secure.
Caesar is considered not very secure.

A-LEVEL Computing - OW (12 decks)

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