1.2 Memory and storage

Question 1

Why do computers need primary storage?

Answer 1

It holds data and instructions which the CPU needs to access while a computer is running. Plus to access this data is faster then secondary.

Question 2

What is the RAM?

Random access memory

Answer 2

Volatile (loses memory when powered off) Holds the operating system, programs and data in use by the CPU.

Question 3

What is the ROM?

Read only memory

Answer 3

Non volatile (doesn’t lose memory when it has no power) Contains the very first instruction for the computer (bootstrap)

Question 4

What is the similarity and difference of RAM and ROM ?

Answer 4

similarities:
- hold information
- Both presented in binary form
Difference:
Ram is volatile Rom is non-volatile
Ram can read and write Rom is read only

Question 5

if the RAM runs out of storage where is data stored?

Answer 5

virtual memory

Question 6

Why might virtual memory be needed in a system?

Answer 6

To allow space in the RAM to store data.

Question 7

What is virtual memory?

Answer 7

non-volatile and secondary memory created to store data when RAM storage is full

Question 8

How does virtual memory work?

Answer 8

Memory is transferred from the RAM to the hard drive where virtual memory is stored .

Question 9

Why do computers need secondary storage?

Answer 9

• it stores the programs when switched off

- back up of data files

Question 10

What is the common types of storage?

Answer 10

Optical
Magnetic
Solid state

Question 11

What are the advantage and disadvantage of optical storage?

Answer 11

Advantages:
-cheap 
- portable
Disadvantage:
- not durability (can easily be scratched)
- speed is slow

Question 12

What are the advantages and disadvantages of magnetic storage?

Answer 12

Advantages:

• cheap
• large capacity
  disadvantages:
• fragile
• slow access time

Question 13

What are the advantages and disadvantages of solid state drives?

Answer 13

Advantages:
- durable
- fast access
Disadvantages:
-expensive 
- limited read and writes

Question 14

What is an example of magnetic, solid state and optical storage?

Answer 14

magnetic - hard disk drive
Solid state - flash memory cards, SSD, memory stick
Optical - DVD and Blu-ray

Question 15

How do you calculate text file size?

Answer 15

Bits per character x Number of characters

Question 16

How do you calculate a sound file size?

Answer 16

Sample rate x duration (secs) x bit depth

Question 17

How do you calculate a image file size?

Answer 17

colour depth x image height x Image width

Question 18

What are the unit of data storage?

Answer 18

The units of data storage:
Bit
Nibble (4bits)
Byte (8 bits)
kilobyte (1,000 bytes or 1KB)
Megabyte (1000 KB)
Gigabyte (1000 MB)
Terabyte (1000 GB)
Petabyte (1000 TB)

Question 19

How do you convert denary to binary?

Answer 19

The table goes from 128, 64, 32, 16, 8, 4, 2, 1 and you start right to left

Question 20

How do you convert binary to denary?

Answer 20

Use the table to add up the values.

Question 21

How do you convert denary to hexadecimal?

Answer 21

You make it binary. Then make it into a nibble (2 sections) then put 1, 2, 4, 8 then add up the values. If the value is 10 or over use the alphabet so A and so on.

Question 22

How do you convert hexadecimal to denary?

Answer 22

The first digit you times by 16 then the second one you add on.

Question 23

What are the rules of binary addition?

Answer 23

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

Question 24

What happens when you shift the binary to the left?

Answer 24

The binary is multiplied by 2

Question 25

What happens when you shift the binary to the right?

Answer 25

The binary is divided by 2

Question 26

What is a character set?

Answer 26

A character set is defined list of characters recognised by the computer.

Question 27

What are 2 examples of character sets

Answer 27

ASCII (extended ASCII) and Unicode

Question 28

what are the total number of characters in ASCII, extended ASCII and Unicode?

Answer 28

ASCII - 2^7 = 128 extended ACSII - 2^8 = 256 Unicode = 2^24 = more then 16 million

Question 29

What is metadata?

Answer 29

Data about Data such as the file format, resolution and colour depth

Question 30

How is the number of colours calculated?

Answer 30

2^n (n being the of bits for each pixel)

Question 31

What is the effect of resolution and colour depth?

Answer 31

The greater the colour depth and resolution the larger the file size of the image.

Question 32

If the sound is stored as analogue what must it be stored as?

Answer 32

It has to be stored in binary.

Question 33

What is sample rate? | + what is the sample rate measured in?

Answer 33

How many samples you take in a second + Hertz

Question 34

What is bit depth?

Answer 34

The number of bits available for each sample.

Question 35

What is the affect of higher bit depth and sample rate?

Answer 35

The higher the number of bit depth and sample rate the higher the quality of sound and the larger the file size.

Question 36

what are the type of compressions?

Answer 36

Lossy and lossless compression

Question 37

Why is data compression used?

Answer 37

To reduce the file size.

Question 38

What is lossy compression?

Answer 38

Removes data permanently which affects the quality of the file.

Question 39

What are the advantages and disadvantage of lossy compression?

Answer 39

Advantage: - Greatly reduces file size - commonly used meaning a lot of software can read lossy files disadvantage: - loses data that affect the quality of the file - can't be used on text

Question 40

What is lossless compression?

Answer 40

Data is removed temporarily and can be restored to its original state.

Question 41

What are the advantage and disadvantages of lossless compression?

Answer 41

``` Advantage: - quality of not affected - can be used on text and software files disadvantages: - only a slight reduction in file size ```

Question 42

Type of file types that lossy compression uses

Answer 42

JPEG and MP3

Question 43

Types of file types that lossless compression uses

Answer 43

PNG and TIFF