1. Computer Systems Nat 4/5 Computing Science
Section 2 Computer Structure:
Lesson 2 :
Memory

2. Lesson Aims By the end of this lesson: Pupils will be able to:
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Lesson Aims
By the end of this lesson:
Pupils will be able to:
Identify the parts of main memory
Describe of the features and uses of RAM and ROM
Describe backing storage
Describe what is meant by addressability

3. Revision Processor Bus Main Memory Bus Nat 4/5
Label the diagram of the processor, buses and main memory

4. A quick recap We are going to look at the Backing Storage and Memory
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A quick recap
Processor
Input Devices
Output
Devices
Memory
Backing Storage
We are going to look at the Backing Storage and Memory

5. Main Memory Main memory falls into two types: RAM RAM ROM
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Main Memory
Main Memory
Main memory falls into two types:
RAM
Random Access Memory
ROM
Read Only Memory
RAM
ROM

6. RAM – Random Access Memory
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RAM – Random Access Memory
Nothing to do with male sheep!
RAM is the computers short term memory.
If a machine is quoted as having 2GB of Ram then it has 2GB into which programs and the operating system is loaded into.
RAM is volatile.
This means that it requires power to store data.
When power is lost the contents of RAM are lost.

7. ROM – Read Only Memory There is a problem with just having RAM.
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ROM – Read Only Memory
There is a problem with just having RAM.
If the contents of RAM are lost then the power is Iost how does the computer know what to do when it switches on?
ROM (Read Only Memory) is memory that will always retain its contents even when power is lost.
This concept can be used by mobile phones to store their operating systems.

8. Addressability Your house has a unique address
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Addressability
Your house has a unique address
No two houses have the same address!
This is the same for a computers memory
Each location in memory has it’s own unique address (memory address).
This means each piece of data ( ) will be stored in it’s own memory location which will have it’s own address
The processor can retrieve any bit of data that is needed. This is known as addressability.

9. Nat 4/5
Backing Storage
Backing storage are devices used to store permanent copies of our files.
Examples are such as:
Hard Disk Drives
USB Flash Drives
Magnetic Tapes
CD/DVD R/RW
At this point in the course knowing their purpose is sufficient.
More on these later!

10. Nat 4/5
Summary
RAM (Random Access Memory) Is used to store programs and the operating system Is volatile, it loses contents when there is no power ROM (Read Only Memory) Contents cannot be changed and does not require power to hold data Addressability The ability to retrieve data from a memory location using it’s address Backing Storage devices are used to store permanent copies of our files and data