1.2

Question 1

State characteristics of secondary storage devices that Nina should consider when choosing a device

Answer 1

Capacity
Speed
Portability
Durability
Reliability
Cost

Question 2

What is meant by the capacity of a storage device

Answer 2

Refers to how much data needs to be stored

Question 3

What is meant by the speed of a storage device

Answer 3

Speed: refers to how quickly can data be read and transferred?

Question 4

What is meant by the portability of a storage device

Answer 4

Portability: refers to if data needs to be transported, are size, shape and weight important?

Question 5

What is meant by the durability of the storage device

Answer 5

Refers to how robust the media is
Will it be damaged by shocks, and extreme conditions?

Question 6

What is meant by the reliability of the storage decice

Answer 6

does it need to be used over and over again without failing?

Question 7

What is meant by the cost of the storage device

Answer 7

how expensive is the media per byte of storage?

Question 8

why data needs to be converted into binary to be processed by a computer

Answer 8

With just two states, electronic components are:

Easier to manufacture

Therefore cheaper

More reliable

Question 9

Examples of using two states to store data:

Answer 9

ram
hard disk
optical disk
flash memory

Question 10

effect of binary left shift

Answer 10

multiply binary number by 2

Question 11

effect of binary right shift

Answer 11

divide binary number by 2

Question 12

remember to circle overflows in the exam and label it - overflow

Question 13

a character set is

Answer 13

A defined list of characters recognised by the computer hardware and software. With each character being represented by a single number

Question 14

examples of character set

Answer 14

Ascii - 7 bit character set
Extended ascii - 8 bit character set
Unicode

Question 15

How are images represented

Answer 15

Each pixel has a specific colour, represented by a specific code

Bitmap pictures are constructed from coloured squares called pixels

an image is represented as a series of pixels, represented in
binary

Each pixel of a bitmap is stored in binary

Question 16

How many colours can 1 bit store
How many colours can 2 bit score

The number of bits required for each pixel depends on the number of colours required

Answer 16

1 bit has 2 possible values: 0 and 1. Therefore 1 bit can store 2 colours: black or white

2 bits have 4 possible values: 00, 01, 10 and 11. Therefore 2 bits can store 4 colours.

Question 17

How can the number of colours be calculated

Answer 17

The number of colours can be calculated as 2n. Where ‘n’ is the number of bits for each pixel

Question 18

What is colour depth

Answer 18

The number of bits for each pixel is known as the colour depth

Question 19

What is metadata

Answer 19

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

Question 20

How to make image quality better

Answer 20

The greater the colour depth and resolution, the larger the file size of the image (and quality of the image)

Question 21

What is resolution

Answer 21

Resolution is the number of pixels in a bitmap image

Question 22

Photographs are stored in 24 bit colour depth
Calculate no. of colours

Answer 22

. Each pixel is stored in 24 bits. This is 2^24 = over 16 million colours

The number of different colours the human eye can see.

Question 23

What affects the quality of a digitally converted sound wave and the file size?

Answer 23

Sample rate (speed)

Bit Depth (detail)

Question 24

what is sample rate

Answer 24

Sample rate:

The number of samples stored per second

the sample rate is the number of times per second the amplitude of the sound wave is measured - measured in khZ
e.g. cd quality is 44.1khz (44,100 samples per second)

Question 25

higher sample rate means

Answer 25

The higher the number of samples per second, the higher the quality of the sound (the better the audio quality as the digital data more closely resembles an analogue wave), and the larger the file size

Question 26

what is bit depth

Answer 26

Bit depth:
The number of bits stored per sample

the number of bits available to represent each sample

e.g. a sample with a bit depth of 4 could be 0101 or 0111 or 1010
A sample with bit depth of 8 could be 01100110

common bit depth is

Question 27

higher bit depth means

Answer 27

The higher the number of bits, the greater the quality of the sound, and the larger the file size

higher bit depth, the more bits are available to be used for each sample. Therefore the quality is often higher as teh wave more closely resembles an analogue wav

file size will be larger, - if the bit depth is higher, as each sample stores additional bits

Question 28

how to calculate file size for sound

Answer 28

The total number of bits in a sound

Calculated as the (Number of samples per second) x (Number of bits per sample) x (Length of sample in seconds)

sample rate (In hertz) x bit depth x duration (in seconds)

Question 29

problem with digital sound wave

Answer 29

digital saplining is discrete (separate) and not continuous like analogue waves
Its lost a lot of data

Question 30

in sound, how can the digital data be improved
how to get highest quality sound

Answer 30

The digital data can be improved by taking samples more regularly
to get the highest quality sound, many samples are taken to recreate the analouge wave as closely as possible

Question 31

what will a low sample rate result in

Answer 31

A low sample rate will result in a low-quality sound because the digital data dos not closely resemble the original analogue wave

Question 32

reasons for compression

Answer 32

Compression reduces the size of a file so it takes up less space.

Maximise the amount you can store on a device.

Smaller files are quicker when transferred (streamed) over the internet.

files take up less storage space (so more files can be stored)
files can be transferred quicker because they are smaller
files can be read from or written to quicker

Question 33

what increases the file sizes of images

Answer 33

number of colours - because we need more bits per pixel to store a greater range of possible colours

Question 34

one way to make image file size smaller

Answer 34

One way to make the file size smaller would be to store a lower number of colours

Or to store bigger areas of pixels as one colour

Both of these techniques will reduce the quality of the image

This is known as lossy compression

Question 35

types of compression

Answer 35

lossy
lossless

Question 36

features of lossy compression

Answer 36

Some of the data is lost and cannot 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 37

FEATURES OF LOSSLESS COMPRESSION

Answer 37

None of the data is lost, it is encoded differently

Can be turned back into original format

Can be used on all types of data

Is usually less effective than lossy compression at reducing the file size

Most suitable for documents and executable files.

Question 38

equation for file size for text files - characters

Answer 38

file size = number of bits per character xnumber of characters

file size in bits

Question 39

file size for images equation

Answer 39

file size = image resolution x colour depth = width x height x colour depth

colour depth also known as bit depth

1 bit represents 2 colours ( black and white)