Lesson Plan
The need for RAM
Teacher’s Notes
Length 60 mins Specifi cation Link 212/i
Learning objective Candidates should be able to:
(i) describe the purpose of RAM in a computer system
Time (min) Activity Further Notes
10 Props: A hard disk drive, CPU and some RAM chips.
Show the students the CPU and, as revision, ask them
to state its function in the computer.
Ask the students where the programs and data are
stored when the computer is switched off.
Show the students the hard disk drive and ask why it is
referred to as a ‘secondary storage device’.
Show the students the RAM chips and reinforce that
program instructions and data being accessed by the
CPU are stored here for quick access.
Using a projector, display the Interactive Starter Activity.
Processes data according to the
instructions provided by the program.
The hard disk drive.
It is a secondary storage device as
programs and data currently being
accessed by the CPU are stored in RAM.
10 Watch the video, pausing to discuss the content.
5 Discuss the video to assess learning. Ask questions
such as:
• Why is RAM said to be volatile?
• Why is it referred to as ‘random’ access memory?
• How is dynamic RAM different to static RAM?
Answers:
Because it loses the data when the power
is turned off.
Because data stored in RAM can be
accessed in any order – does not have to
start at the fi rst address and go through in
a serial search.
Dynamic RAM has to be continuously
recharged or refreshed or it loses the data.
To store a ‘1’ the memory location has to
be charged with electrons. But in dynamic
RAM the memory locations are ‘leaky’ and
lose electrons, so could empty and therefore
represent a ‘0’. Therefore thousands of
times a second the CPU has to read each
memory location and reset it to ‘1’.
Static RAM does not need continuously
recharging and is therefore much quicker
– data can be accessed by the CPU more
rapidly.
Static RAM, however, is far more expensive.
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