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