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Memory and Storage

This lesson explains the difference between the two types of primary memory, RAM and ROM, and how they differ from secondary storage. You will learn the three secondary storage technologies and what virtual memory is used for.

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RAM versus ROM

RAMROMVolatileloses data at power offNon-volatilekeeps data at power offRead + writecurrent data + programsRead onlyboot-up / BIOSBoth are primary memory the CPU reaches directly
  • RAM (Random Access Memory) is volatile, which means it loses its contents when the power is switched off.
  • RAM holds the data, programs and parts of the operating system that are currently in use, and its contents can be read from and written to.
  • ROM (Read Only Memory) is non-volatile, so it keeps its contents even when the power is off.
  • ROM usually stores the boot-up instructions, such as the BIOS, that the computer needs to start, and these are not normally changed by the user.

Check you've got it

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1. Which statement about RAM and ROM is correct?

2. Which of the following is an example of magnetic secondary storage?

3. How does an optical storage device such as a CD or DVD read the data stored on it?

4. Why is virtual memory used in a computer system?

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