Data Representation

Question 1

What are the three types of files?

Answer 1

Text
Sound
Image

Question 2

How do you calculate text file size?

Answer 2

Bits per character x number of characters

Question 3

How do you calculate the size of sound files?

Answer 3

Sample rate x duration(s) x bit depth

Question 4

How do you calculate the file size for image files?

Answer 4

Colour depth x image height(px) x image width

Question 5

What is an overflow error?

Answer 5

An overflow show that the result of the calculation is too big for it to be stored in 8 bits

Question 6

What are the rules of binary addition?

Answer 6

0 + 0 = 0
0 + 1 = 1
1 + 1 = 0 carry 1
1 + 1 + 1 = 1 carry 1

Question 7

What does the result of one left shift leave?

Answer 7

The original number is multiplied by 2

Question 8

What does one right shift produce?

Answer 8

The original number is divided by 2

Question 9

What is a character set?

Answer 9

A defined list of characters recognised by the computers hardware and software. Each character is represented by a single number.

Question 10

What are examples of character sets?

Answer 10

ASCII - American standard code for information interchange- 128 character
Extended ASCII- 256 characters
Unicode- 16 million character

Question 11

What is metadata?

Answer 11

Metadata is additional data stored with the images to define the width, height, colour depth and colour palette

Question 12

What are the two types of compression?

Answer 12

Lossy
Lossless

Question 13

What are some effects of lossy compression?

Answer 13

Some of the data is lost and can’t be recovered
Greatly reduces the file size
Reduces the quality of the image/ sound
Suitable for images, sound and video
Cannot be used on text and executable files

Question 14

What are some effects of lossless compression?

Answer 14

None of the data is lost, it is just encoded differently
Can be turned back into original format
Can be used on all types of data
Usually less effective than lossy compression at reducing the files size
Most suitable for documents and executable files

Question 15

Need for primary storage

Answer 15

Main memory is required to temporarily store the programs, instructions and data the computer needs whilst in operation.

Question 16

Ram properties

Answer 16

Volatile- all data lost
Can be written to, and read from
Used for the computers working memory for instructions, programs and data

Question 17

Rom properties

Answer 17

Non volatile- data permanently retained without power
Used for the computer start up instructions and in embedded systems.
Read on,y so cannot be written to

Question 18

Define virtual memory

Answer 18

Virtual memory is used when there simply isn’t enough space in RAM for all programs and data you are currently working on

Question 19

Why secondary storage

Answer 19

Need secondary storage for longer term storage of files and data because it is non volatile

Question 20

What is a bitmap?

Answer 20

Made up of picture elements or pixels

Question 21

Advantages of lossy

Answer 21

Smallest file size, least transmission time, reduces internet traffic and collisions

Question 22

Disadvantages of lossy

Answer 22

Detail is permanently lost

Question 23

Advantages of lossless

Answer 23

Original quality is preserved

Question 24

Disadvantage of lossless

Answer 24

Less significant reduction in file size

Question 25

Example of lossless

Answer 25

Text file