CS32 : How Computers Remember

A close look at primary storage and how this is used to help the computer keep running.

We are learning ...
  • About different types of primary storage and their applications
So that we can ...
  • Show an understanding of the difference between primary, secondary and off-line storage
  • Explain the meaning and purpose of RAM and ROM
  • Explain the purpose for and characteristics of cache memory
  • Explain the need for virtual memory

CGP The Revision Guide Page 4
CGP Exam Practice Workbook Page 7

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Click me to start!
Define the key terms!
It's revision!

Activity 1
Different types of storage 

Memory is crucial to the operation of computer systems (and humans, especially if you are taking exams!)

Task 1.1 Memory Game
Where we learn that humans can only remember a limited amount

If you are lucky, your teacher will give you a set of 'Memory cards'. If not, you can download it by clicking the link. Practice it with your shoulder partner - what strategy did you use?

Type of storage

There are three common types of storage technology. Each is used for different things.

Task 1.2 Comprehension
Where we learn about the characteristics of different types of storage


Read the following passage of text, carefully. You could read it out loud to your shoulder partner.

Types of storage

RAM is a type of fast access memory connected directly to the computers motherboard. RAM is classed as 'primary storage' or an 'immediate access store' because it is used directly by the computer when it is operating. The term 'RAM' stands for 'Random Access Memory' which means that any location in memory can be accessed directly at any time, you don't have to store the next item in the next space like you might have to with magnetic tape for instance.  RAM holds programs that are currently running and the data that they are accessing. RAM is temporary storage; it loses it's contents when the power is switched off. The processor itself also contains both extremely fast access 'registers' and a small amount of very fast RAM called 'cache' (pronounced 'cash') memory. The processor stores commonly used instructions / data in this for fast access during it's operation.

ROM is similar to RAM except that it does not lose it's contents when the power is switched off. The term 'ROM' stands for 'Read Only Memory' indicating that it's contents cannot (easily) be changed. The computer uses as special program held in ROM called a 'bootstrap loader' to start the hardware and load the operating system when the computer is started up. This is called the Basic Input Output System, or BIOS.

Long term, semi-permanent storage is provided by 'secondary storage' devices like hard disk drives. Hard disk drives hold data which are not currently being used by the processor but may be required at some stage during operation. Secondary storage devices are slower than primary storage devices which is why they are not used for programs currently in operation. However, if the primary storage starts to get full, 'virtual memory' is created in a 'paging file' on the secondary storage device to augment the physical memory. This can considerable slow down the computer operation.

Offline storage include removable storage media such as magnetic tape, CD, DVD, Bluray and memory sticks. Removable storage are suitable for storing multimedia files, distributing software and archiving / backup. Magnetic and optical media require separate hardware 'drives' to read them whereas memory sticks usually connect via USB.

Demonstrate your understanding

Answer the following questions in full sentences in your notebooks / on paper.
  1. What does the term 'RAM' stand for?
  2. Why is RAM given this name?
  3. What is the purpose of RAM?
  4. Where is 'cache' memory?
  5. What does the term 'ROM' stand for?
  6. State one use for ROM in a computer system.
  7. Use the World Wide Web to find out what the acronym BIOS stands for.
  8. What might happen if usable RAM starts to run out?
  9. What implication might this have on the operation of the computer?
  10. What does the term 'offline' mean?
  11. What is offline storage used for?

Activity 2
Virtual memory

Sometimes, there just isn't enough physical primary storage (memory) for all the programs that need to run. Computers can be configured so part of the hard disk drive behaves like main memory, known as 'virtual memory'. This isn't ideal because the read / write speed of hard disks is very much slower than main memory. Virtual memory is used to store parts of programs current being run but not executed. As the processor gets to the next part of the program, chunks are 'paged' or 'swapped' between main memory and virtual memory.

Task 2.1 How much RAM?
Where we learn how much virtual memory our computer has

In your notebooks

Virtual memory is in fact a hidden, system file called pagefile.sys on the computer system.  The page file is generally the same size as the physical RAM on a computer.  How much physical RAM has my laptop got? Write down your ideas in your notes.


Virtual memory is a little bit like an overflow car park.  Often, the main car park is tarmac, easy access, dedicated spaces and near to the venue.  Overflow parking is often on muddy fields further away from the venue. Can you explain the analogy in your own words in your notebooks / on paper?

Task 2.2 How fast?
Where we learn to compare the access speed of different storage devices

On the worksheet

Download and complete the worksheet 'How fast' and hand it in to your teacher for assessment.

Activity 3

When you are in the middle of a piece of work at school and your 'friend' turns off your computer, you will notice (!) that you lose all the work you did since the last time you saved it. This is because the work since the last save is held in RAM and RAM is volatile because it looses it's contents when the power is switched off. Hard disk drives are designed for longer term storage and are non-volatile.


Task 3.1 Volatility
Where we learn to categorise volatile and non-volatile storage devices

Representing ideas as a table

Use a table to categorise the following storage devices as volatile or non-volatile.

Assessment Task (Homework)

You have a choice for this task. There is a lot of information on this page that you need to learn. However, words often don't help you remember the information. So, your task is to convert all the information into either ...
  • Picture(s) with no more than 32 words;
  • Podcast lasting no longer than 2:30s;
  • Video lasting no longer than 2:30s;
  • Cartoon strip with 12 boxes;
  • A poem with 5 verses.
Present your response to your teacher in which ever way you see fit.

Grading rubric

MASTER : You have substantially changed the information from this section.
APPRENTICE You have partially changed the information from this section.
NOVICE : You have barely changed the information from this section.

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Click to load key word list to help you make your own flash cards 

Hungry for more?

Try the following memory game. It's written in HTML5, CSS and Javascript and hosted on Codepen.io so you can experiment with it to change it if you want.

Click to load the pen