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:
Describe the difference between main memory and backing storage
Describe some of the features and uses of RAM and ROM
Describe what is meant by a memory address

3. Nat 4/5
A quick recap
Memory
Processor
Input Devices
Output
Devices
Backing Storage
ROM
RAM
We are going to look at the Backing Storage and Memory

4. 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

5. 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 are loaded into.
RAM is volatile.
This means that it requires power to store data.
When power is lost the contents of RAM are lost.

6. 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.

7. 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 memory
Each location has a unique address

8. 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!

9. Summary RAM (Random Access Memory) ROM (Read Only Memory)
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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
Backing Storage devices are used to store permanent copies of our files and data