1.2 Units of Information

Question 1

What does Primary storage do

Answer 1

It holds the data and instructions which the CPU needs access to while a computer is running.

Question 2

What does Primary Storage Consist of

Answer 2

Random Access Memory (RAM)
Read Only Memory (ROM)
Registers & Cache

Question 3

What is RAM

Answer 3

• Holds the operating system, programs and data in use by the CPU when the computer is running.
• Volatile (contents lost when the power is turned off).
• Read and write.
• Large in comparison to ROM.

Question 4

What is ROM

Answer 4

• Holds the first instructions for when the computer is first turned on known as the bootstrap.
• Programs may by stored in ROM in embedded systems.
• Non-volatile (contents remains when power is turned off)
• Read only
• Small in comparison to RAM

Question 5

What is Virtual Memory used for

Answer 5

• Virtual memory is needed when there is not enough physical RAM to store the open programs.
• Virtual memory is held on the hard disk.
• Programs are transferred out to virtual memory from the RAM when they are not currently being executed.
• Programs are transferred back to RAM from virtual memory when they are needed.

Question 6

What is secondary storage needed for

Answer 6

• Secondary storage is needed because ROM is ready only and RAM is volatile.
• Second storage is needed for:
  Storage of programs and data when the power is turned off. Semi-permanent storage of data that can change.
  Backup of data files.
  Archive of data files.

Question 7

What are the common types of Storage

Answer 7

Optical (CD-R, DVD-R)
Magnetic (Hard disk drive)
Solid state (SSD, Memory stick)

Question 8

What are qualities of Optical storage

Answer 8

Low capacity compared to other types of storage.
Slow to access data.
Thin, lightweight and portable.

Question 9

What are qualities of Magnetic Storage

Answer 9

High storage capacity.
Quick to access data.
Has moving parts, which eventually fail.
Hard disks perform better if they are defragmented

Question 10

What are qualities of Solid-State Storage

Answer 10

Medium storage capacity.
Very quick to access data.
No noise. No moving parts, very reliable.
Low power.
No need to defragment.
Limited number of read/write cycles.
Expensive compared to other types of storage.

Question 11

How do you calculate text file size

Answer 11

Bits per character x number of character

Question 12

How do you calculate image file size

Answer 12

Colour depth x image height px x image width px

Question 13

How do you calculate sound file size

Answer 13

sample rate x duration in second x bit depth

Question 14

Why do computers use Binary

Answer 14

• Easier to manufacture
• cheaper
• more reliable

Question 15

What is a character set

Answer 15

a defined list of characters recognised by the computer

Question 16

What is ASCII

Answer 16

7 bit character set with 128 characters (2^7)

Question 17

What is Extended ASCII

Answer 17

8 bit character set with 256 characters (2^8)

Question 18

What is UNICODE

Answer 18

24 bit character set with > 6 million characters (2^24)

Question 19

What can images be stored as in binary

Answer 19

Bitmap
Vector

Question 20

What are Bitmap pictures

Answer 20

Pictures constructed from coloured squares called pixels

Question 21

What are Vector pictures

Answer 21

Pictures that store the mathematics to draw coloured shapes

Question 22

What is the general formula to find the number of colours

Answer 22

2^n (n=number of bits for each pixel)

Question 23

What is metadata

Answer 23

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

Question 24

How do you calculate a sound file size

Answer 24

number of samples per second x number of bits per sample x length of sample in seconds

Question 25

What is a sound file

Answer 25

the total number of bits in a sound

Question 26

What is bit depth

Answer 26

The number of bits stored per sample

Question 27

What is sample rate

Answer 27

The number of samples stored per second

Question 28

What is compression

Answer 28

Reducing the number of bits in a file
Making the storage capacity of the file lower
Making data transfer of the file quicker

Question 29

What is lossy compression

Answer 29

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 30

What is lossless compression

Answer 30

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.