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Flashcards in Data Deck (76):
1

name the order of units from smallest to biggest (bytes)

bits
nibble
bytes
kilobytes
megabytes
gigabytes
terabytes

2

how many bytes are in 5 megabytes

5 x 1024 x 1024 = 5,242,880

3

explain the effect of increasing the sampling frequency for a sound conversion

- more data will be converted
- therefore increases the storage capacity for the recording
- this will be a more accurate representation of the original recording

4

compare storing data on the cloud to on hard disks for a school

- school is responsible for providing more storage as demands evolve but storage provider is responsible for providing storage on demand

- if internet connection isnt available, cant access data on the cloud but files are available without a connection on hard disks

- staff can access data anywhere using mobile devices on cloud but data can be only accessed in the school

5

how do computers read program instructions

- processors contain billions of transistors which act as switches.
- they only have 2 states - on and off
- there are only 2 states therefore binary is used to represent data and instructions

6

how are pictures represented in binary and why

- in black and white (no colours/shades) because there are only two digits used

7

write an arithmethic expression to show that 256 different colours can be represented in 8 bits

number of colours = 2^8 = 265 colours

8

how many colours can be represented in 6 bits

2^6 = 64 colours

9

how many bits does it take to represent 16 colours

16 = 2^4 so it takes 4 bits

10

convert 79 into binary

01001111

11

convert 00110110 into denary

54

12

convert 203 into binary

11001011

13

what is an overflow error

an overflow error occurs when a calculation produces a result that is greater than the processor can deal with

14

state an effect of using the result of the overflow error in further calculations

the calculations would produce inaccurate results

15

add 01011101 and 01011001

10110110

16

convert 10010111 into a decimal number (denary)

151

17

how many shifts to the left would you shift a binary number if you mulitply it by 2^4

4 places

18

how do you perform a logical shift (multiplying)
what effect does this have on the number

Left Logical muLtiply

move the digits to the LEFT and fill the gaps with 0s
multiplys the number by a power of 2 ie 2^3 is 3 shifts. number would be 8 times bigger

19

explain how a binary number can be multiplied by 8 by shifting bits

8 is equal to 2^3 so the bits are shifted 3 places to the left
0s should replace the 3 gaps on the left

20

multiply 01101110 by 2^3

01110000

21

how do you perform a logical shift (dividing)
what effect does this have on the number

dIvIde = rIght

move the digits to the RIGHT and fill the gaps with 0s
divides the number by a power of 2 ie 2^3 is 3 shifts. number would be 8 times smaller

22

explain why performing a logical shift of 3 places on the binary number 10110100 could result in a loss of precision

- 10110100 = 180.
- the calculation would be 180/8 = 22.5
10110100 shifted is 00010110 (this is 22 which is less than 22.5)

this is because the answer is always given as the nearest lower integer in a right logical shift so some precision is lost

23

how do you represent a denary number in sign and magnitude

the leftmost big (MSB) is used to show that a number is positive (0) or negative (1) and is shown +/-
the other 7 bits show the numerical value of the number

24

convert -62 into binary

11000010

25

convert 62 into binary using sign and magnitude

00111110

26

how do you represent a denary number in twos complement

the leftmost big (MSB) is used to show that a number is positive (0) or negative (1) and is shown as -128
the other 7 bits are posistive
- highest denary number you can represent is 127

27

give disadvantages of sign and magnitude

0 can be both posistive and negative
when adding +10 and -10 the result should be 0 but it gives -20

28

give advantages of twos complement

- 0 can be represented in only one way 00000000
- calculations are always accurate
- negative numbers can be represented

29

give disadvantage of twos complement

computers cannot use this number system only humans

30

give a disadvantage of sign and magnitude

computers cannot use this number system only humans

31

whats the highest number you can represent in bianary

255
to get a higher number you must add more bytes

32

compare using binary to twos complement

- binary can be used by computers, twos complement cannot

- binary can represent higher denary numbers (255) than twos complement (127)

- two complement can represent negative numbers, biary cannot

33

state 2 reasons why using twos complement is preferable to sign and magnitude

- 0 can be represented in only one way 00000000
- additions are always accurate

34

how do you subtract in binary

- turn number into its negative form by flipping all the bits (1s to 0s) and adding 1
- add the 2 numbers together

35

01000110 - 01000110

01000110 = 70
+ 1
10111010 = -70

10111010
+ 01000110
I NEED WORK

36

how do you multiply signed binary numbers

- perform arithmetic shift left
- shift the bits LEFT and fill the gaps with 0s
- never move the MSB as this determines the sign
- used in sign and magnitude to multiply it by a power of 2

37

perform an arithmetic shift left on -36

36 = 00100100
MSB stays where it is (36 is posistive)
72 = 01001000

38

perform an arithmetic shift left on 36

-36 = 11011100
MSB stays where it is (-36 is negative)
-72 = 10111000

39

how do you divide signed binary numbers

- perform arithmetic shift right
- shift the bits RIGHT and fill the gaps with copies of the MSB
- never move the MSB as this determines the sign
- used in twos complement to divide it by a power of 2

40

perform an arthimetic shift right 3 places on 01101011 in twos completment

0001101

41

how do you convert 10110011 into hexadecimal

spilit the byte into 2 nibbles:
- 1011 = 8+2+1 = 11
11 is B
- 0011 = 2+1 = 3
B3

42

What do the letters in hexadecimal represent

A = 10
B = 11
C = 12
D = 13
E = 14
F = 15

43

convert C3 to binary

split hexadecimal in 2
C = 12 1100
3 0011

11000011

44

what are the uses of hexadecimal

- to help humans to cope with long strings of binary digits (much shorter than binary)
- to give error code messages when a computer malfunctions
- to represent numerical values in assembly language (a low-level programming language)
- used in true colour

45

what is true colour

- it uses 24 bits to code every available colour variation (2^24)
- each one represented by 3 8-bit numbers, simplified to 3 hexadecimal numbers
- this is far easier to remember & enter 6 hexadecimal digits than 24 digits of binary

46

what is ascii code

- a 7 bit code with 2^7 (128) code sequences
- represents characters, numbers, text and symbols ie shift and space
- the character set is the list of binary codes that can be recognised by computer hard/software

47

what is the extended ascii code

- uses 8 bits with 2^8 (256) code sequences
- includes maths symbols ie π

48

what is are the disadvantages and advantages of extended ascii code

+ can represent more code sequences than the standard ascii code

- data cannot be transferred across platforms accurately as it hasn't been standardised like standard ascii code so different manufacturers use different codes for different characters

- not enough codes to represent different languages

49

how do you find different characters in ascii code

- if you know lower case 'a' is 97 then 'c' is 99
- if you know upper case 'S' is 83 then 'W' is 87

50

how do you return ascii code in PYTHON pseudocode

- ord('c') returns 99
- chr(100) returns 'd'
- cannot do this in edexel pseudocode

51

the character at index (2) returns the number 99 and index(3) returns 101
what numbers would be returned at index (8)

110

52

what is a pixel

short for picture element.
- a digital image composed of many small points of colour
- each pixel has its indivudual colour
- the greater the number of pixel, the greater the detail in the picture

53

how do you write the size of an image

width x height
ie 300 x 1000

54

what is colour depth

the number f bits used to encode the colour of each pixel
- the more bits used to encode the colour the greater of actual colours that can be representted in the images. image is more detailed

55

what colour depth do modern cameras and spartphones use

24-bit colour depth = 2^24 colours

56

how do you work out the image file size

width x height x colour depth (IN BITS)

- the better the image quality the larger the file size
- large file sizes can be problematic when sending them electronically or when storage space is limited

57

what is the resolution of an image

the number of pixels per inch when the image is displayed

58

what happens if a small image becomes enlarged

- it is less sharp as there are less pixels per unit of area and each pixel has to be enlarged
- therefore image has a lower resolution
- if it is enlarged too much it becomes pixelated meaning individual pixels can be seen

59

contruct an expression to calcuate the file size in MB of a 24 bit image with the dimensions 410 x 270

convert into MB
(410*270*24)/8/1024/1024

60

describe what factors affect the quality of a digital image

- the number of pixels that make the image up
- an image of 5000 x 3000 will have a better resolution than an image with size 640 x 480 pixels
- number of bits used to encode the colour of each pixel is called colour depth. if more bits are used, more colours can be displayed
- if more colours are used then v. small colour changes can be represented in the image, increasing the detail

61

how are all images represented in computers

strings of 1s and 0s

62

how is sound represented in digital form

strings of 1s and 0s

63

describe how an analogue recording is performed

- sound is caused by vibrations travelling through a medium ie air or water
- sound recordings convert the changes in air pressure into voltage changes

64

what is the sampling frequency

how many samples of a sound wave are taken per second (measured in Hz)
- a high sampling frequency gives a more accurate reproduction of the analogue waveform

65

what is a sample in sound recording

- snapshots of the sound at regular fixed intervals. these samples are played back one after the other, known as a digital recording
- digital recordings cant continuously reproduce analogue changes since transistors can only be on or off

66

what is the bit depth/resolution of a sound recording

the number of bits used to encode each sample
- high bit depth allows more data to be stored and allows the dynamic range of the sound to be more accurately represented
- 8 bits allows 2^8 graduations of volume

67

what is the sampling frequency for CDs

44100 Hz

68

what is the sampling frequency for bluray audio

96000 Hz

69

how do you convert from bytes to KB

x 1024

70

how do you convert from MB to TB

x 1024 x 1024

71

how do you calculate audio file sizes

file size (BITS) = sample freq x bit depth x recording length (SECONDS)

- higher the sample freq and bit depth larger the file size
- if storage availability is low, lower sample rates must

72

what happens if storage availability is low for sending for storing audio files

- lower sample rates must be used, lowering the accuracy of the digital representation of the analogue signal and lowering the quality of the recording

73

what is KHz equal to in Hz

1000Hz

74

construct an expression to caculate the size in MB of a digital audio file of 3 minutes with a sampling frequency of 44.1 KHz and resooution of 16 bits

convert units
(44100 x 180 x 16)/8/1024/1024 MB

75

how do you convert from bits to MB

x 8 x 1024 x 1024

76

contruct an expression to calculate the file size in MB of a stereo audio file if duration is 2 mins 30 secs and sampling freq is 44.1KHz with bit depth of 16 bits

(150 x 44100 x 16 x 2)/ 8/ 1024/ 1024
stereo recordings have 2 channels therefore total file size must me DOUBLED