The CPU, internal memory and backing storage Cambridge IGCSE Information & Communication Technology revision
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In plain words
Whatever its size, a computer has the same main parts: something to do the processing, somewhere to hold what it is working on, somewhere to keep things permanently, and ways for data to get in and out.
6 things to know
- The central processing unit (CPU) processes the instructions and data entered into the computer in order to produce an output.
- RAM (random access memory) holds the data and programs in use at the moment. It can be read and written to, and it is volatile: its contents are lost when the power is switched off.
- ROM (read only memory) holds the instructions needed to start the computer. It can only be read, and it is non-volatile: its contents are kept without power.
- Input devices enter data into the computer. Output devices show or send out the results of processing.
- Backing storage holds data and programs permanently. It is non-volatile, it has a much larger capacity than internal memory, and it is slower to access.
- Internal memory is directly accessed by the CPU and is fast but small. Backing storage keeps data when the computer is off.
Worked example
A student is typing an essay when the power fails. The essay had not been saved. Explain why the work is lost, and why the saved files are not.
- The essay was being held in RAM while it was worked on.
- RAM is volatile, so its contents were lost when the power went off.
- Saved files are on backing storage, which is non-volatile, so they are still there.
Tips and tricks
- Volatile means "loses its contents when the power is turned off". Use those words.
- RAM and ROM are both internal memory. Hard disks and solid-state drives are backing storage, not memory.
It lands in your notebook with its questions as flashcards.
The CPU, internal memory and backing storage: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is the role of the CPU?
It carries out the instructions of programs.
What does volatile mean?
RAM is volatile. ROM and backing storage are not.
Which holds the instructions needed to start the computer?
ROM is non-volatile, so the instructions are always there.
Which statement about RAM is correct?
It is the computer's working memory.
Why does a computer need backing storage?
RAM loses everything without power.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
2 questions, 6 marks. Write your answers on paper, then check them.
The CPU, internal memory and backing storage
Cambridge IGCSE Information & Communication Technology 0417 · 6 marks · papermunch.org
Name ______________________________ Date ______________
Give two differences between RAM and ROM.[4]
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RAM is volatile, but ROM is non-volatile. RAM can be written to and read from, but ROM can only be read. (Also: RAM holds data in current use, but ROM holds the start-up instructions.)
Give two differences between backing storage and internal memory.[2]
Show answerHide answer
Backing storage keeps its data when the power is off, but RAM does not. Backing storage has a larger capacity and is slower to access.
Answers: The CPU, internal memory and backing storage
- 1. RAM is volatile, but ROM is non-volatile. RAM can be written to and read from, but ROM can only be read. (Also: RAM holds data in current use, but ROM holds the start-up instructions.)
- 2. Backing storage keeps its data when the power is off, but RAM does not. Backing storage has a larger capacity and is slower to access.