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Memory and storage
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Computers use several kinds of memory and storage, each balancing speed, size and cost.
RAM and ROM
RAM holds the programs and data currently in use. It is volatile: its contents are lost when power is off.
ROM holds instructions needed to start the computer. It is non-volatile and usually read-only.
ROM holds instructions needed to start the computer. It is non-volatile and usually read-only.
Secondary storage
Non-volatile storage for files and programs.
Virtual memory
When RAM is full, part of secondary storage is used as virtual memory.
Secondary storage is much slower than RAM, so the computer slows down. Adding more RAM helps.
Secondary storage is much slower than RAM, so the computer slows down. Adding more RAM helps.
Why does a laptop for travel usually use an SSD instead of a hard disk drive?
- An SSD has no moving parts, so it is not damaged by knocks.
- It is faster and uses less power, saving battery.
- So it suits a portable device.
Answer: It is more robust, faster and uses less power.
RAM is volatile working memory; ROM is non-volatile startup memory. Secondary storage is magnetic, optical or solid state. Virtual memory uses storage when RAM is full, which is slow.
The interactive lesson includes the diagrams for this topic.
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