ROM stores permanent instructions for starting up a computer system, while RAM is used as temporary memory for active programs and data. RAM is volatile and loses data when powered off, while ROM is non-volatile. Virtual memory allows a computer to temporarily store data from RAM onto disk storage when physical memory is low, making more memory available to programs than is physically installed. Cache memory holds recently used data from RAM and main memory to improve CPU performance. Flash memory is non-volatile like ROM but can be rewritten electrically like RAM.

1. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Memory
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2. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
What is
memory?
What is ROM
and RAM?

3. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
ROM and RAM
• The main internal memory in
a computer can be split into
two types:
– ROM (Read Only Memory)
– RAM (Random Access
Memory)
3
5 mins

4. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
ROM
• As the name (Read Only Memory) suggests, this
memory that cannot be changed by a program or user.
• It is used to store the instructions for the computer to
start up when it is turned on again.
• The data in the ROM is saved even if the computer is
switched off and this is known as “non-volatile” data.
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5. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
RAM
• RAM is much faster than ROM and is used as a
temporary memory in which programs,
applications and data are stored whilst they
are being used.
• If a computer loses power, all data stored in its
RAM is lost, this is known as “Volatile” data.
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Secondary
Storage
RAM
Cache
Memory
CPU

6. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Size of Cache
• The more cache memory there is, the more
likely that the data will have already been
requested from the main memory and placed
into the cache. Therefore, it is less likely it will
have to be retrieved from the main memory
so the CPU can run faster.
• The cache memory is very fast but also very
expensive so it is a lot smaller than the main
memory in a computer.
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MEMORY

7. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Levels of Cache
Generally there are three levels of cache memory:
• Level 1
– This is usually located on the CPU chip itself but has a very low
capacity and runs at the same speed as the CPU.
• Level 2
– This is a little further away from the CPU and is larger but slower than
the CPU.
• Level 3
– This is the largest of the three levels but also the furthest away and
therefore the slowest.
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MEMORY

8. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Flash Memory
• ROM uses a similar group of transistors wired together to make a
circuit that are programmed with the instructions to boot up the
machine at the point of manufacture.
• These circuits trap electrons in the transistors using a large
“flash” of electrical charge. This is where it gets its name from.
• It is the same technology used in removable
storage devices such as a USB memory stick.
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9. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Flash Memory
• Remember: ROM stands for Read Only Memory and is
used for the instructions used to boot up the computer.
• Flash memory sticks are used to write and re-write files
time and time again and this writing and re-writing can
cause the circuits to deteriorate over time so flash
memory sticks should not be used in critical systems.
9

10. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Virtual Memory
• Virtual memory is a feature of an operating
system (OS) that allows a computer to
compensate for shortages of physical memory
by temporarily transferring pages of data from
random access memory (RAM) to disk storage.

11. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Virtual Memory
• Primary memory has a limit i.e how many RAM chips you have in
the computer. But there is a trick that the memory manager can use
to fool the operating system into thinking that there is more
primary memory than is actually physically present. This trick is
called virtual memory.
• When the computer is running short of physical primary memory
e.g. too many applications open, the memory manager has a
choice. It can either shut down applications (very inconvenient) or it
can try and source some more memory from somewhere else. This
is where virtual memory comes in.

12. All of you will: Describe the difference between ROM and RAM. GRADE D-C
Most of you will: Explain the need for ROM in a computer. Explain the purpose of RAM in a
computer and how this affects the performance of the computer. Describe how flash memory
works. GRADE C-B
Some of you will: Explain the need for virtual memory. Explain how the developments in
memory research are affecting the future of memory storage. GRADE B-A
Exam Style Questions
Describe the difference between RAM and ROM
Explain the need for ROM in a computer system
Describe the purpose of RAM in a computer system
Explain how the amount of RAM in a personal computer affects the
performance of the
computer
Explain the need for virtual memory
Describe cache memory
Describe flash memory