1.2: MEMORY AND STORAGE 3.0

Question 1

explain the effects of performing a 2 place right shift on a binary number:

Answer 1

• divide by 4

- loss of accuracy/ precision (bits on the right are removed)

Question 2

What is the purpose of data compression?

Answer 2

-reduces the size of a file stored on secondary storage.

Question 3

Advantages of data compression: (2)

Answer 3

• smaller files are easier to transmit across a network as they require fewer packets to be sent.
• their reduced size means more files can be stored in the given area of storage.

Question 4

What are the two types of compression?

Answer 4

• lossy compression

- lossless compression

Question 5

What happens with lossy compression? and what does it result in?

Lossy compression standards (file formats):

Answer 5

• some data is removed and discarded, thereby reducing the overall amount of data and the size of the file.
• JPEG, MPEG, MP3

Question 6

What happens with lossless compression?

lossless compression standards (file formats):

Answer 6

• files are reduced in size without the loss of data

- PDF (text documents), GIF (image file format)

Question 7

Give an example of how lossy compression can affect the quality of a file:

Answer 7

-reduction of colour depth in a JPEG image

Question 8

what does a character set (as a group) assign? and what does it enable the computer to do (2)

Answer 8

• group of code that assign a character to a unique bit pattern,
• which enables the computer to understand and display it

Question 9

what does a character set consist of?

Answer 9

-all the letters, numbers and special characters that can be recognised by a computer system

Question 10

2 common character sets:

Answer 10

• ASCII

- Unicode

Question 11

what does ASCII use and what does it provide?

Answer 11

• 8 bits

- character set of 256 characters

Question 12

what is a possible problem that might be encountered with ASCII?

Answer 12

-256 characters is far too small to hold every character in other languages or contain custom characters

Question 13

what does Unicode use and what does it provide?

Answer 13

• 16 bits

- character set of 65,536 characters

Question 14

what does Unicode use that makes it more efficient?

what could Unicode’s larger character set be used to represent?

Answer 14

• uses more bits, thereby providing a larger character set

- characters from foreign languages and custom characters

Question 15

how are character sets ordered?

Answer 15

logically

Question 16

what is the number of characters stored limited by?

Answer 16

of bits available

Question 17

what is a bitmap? and what happens to it when it is scaled up? (2)

Answer 17

• image made of pixels

- it blurs when scaled up

Question 18

what are digital images made up of?

Answer 18

pixels.

Question 19

what is ‘pixel’ short for? what does each pixel have? and what is it encoded in?

Answer 19

• picture element

- each pixel has a single colour which is encoded in binary.

Question 20

what is each pixel represented by?

Answer 20

a binary number.

Question 21

what does the number of bits determine? (in an image)

Answer 21

-the range of colours.

Question 22

what is resolution? and what is it expressed as?

what is resolution a measure of?

Answer 22

• number of pixels that an image contains
• height and width

-how tightly packed the pixels are.

Question 23

Describe how bitmap images are represented in binary: (3)

Answer 23

• image is composed of/ split up into pixels.​
• each pixel is encoded with a binary code which represents the colour of that pixel.​
• each colour is assigned a unique bit pattern.​

Question 24

what is colour depth?

Answer 24

bits per pixel used to represent a colour

Question 25

what is the correlation between the colours an image requires and bit depth (bits per pixel). what does this result in and why? (2)

Answer 25

• the more colours an image requires, the more bits per pixel are needed.
• a larger file size as more data is stored

Question 26

what does higher resolution result in? and why?

Answer 26

a bigger file size as more data is stored

Question 27

characteristics of a low resolution image: (2)

Answer 27

• has less pixels, which means that the pixels are larger and therefore, fewer are needed to fill the space.
• this results in images that look blocky or pixelated (an image of lower quality)

Question 28

characteristics of a high resolution image: (2)

Answer 28

• has more pixels, which means that the pixels are smaller and can provide a more accurate depiction of the image (as they can display all minute details-including the full range of colours-visible to the naked eye)
• this results in the image appearing to be of higher quality, irrespective of whether it is enlarged or stretched.

Question 29

which factors affect the quality and size of an image?

Answer 29

resolution and colour depth

Question 30

what happens when colour depth and resolution are increased? and vice versa? (2)

Answer 30

increased: relative quality of image increases, but so does file size
decreased: relative quality of image decreases, but so does file size