Storage and Memory
Computers store data in memory hierarchies.
About this topic
Computers use different kinds of memory arranged in a hierarchy. Registers and cache are tiny and extremely fast, RAM is larger and fast but volatile, and secondary storage such as SSDs and hard drives is large and permanent but slower. Capacity is measured in bytes, with a kilobyte, megabyte, gigabyte and terabyte each roughly a thousand times larger than the last.
The tradeoff is speed, size and cost: the faster the memory, the more it costs per byte, so computers use a little fast memory and a lot of slow memory. Hard drives store data magnetically on spinning platters, SSDs use flash memory with no moving parts, and optical discs use lasers. Cloud storage keeps files on remote servers.
A single photo of 3 MB means a 64 GB phone can hold roughly twenty thousand of them, while the RAM needed to edit one is much smaller. A common misconception is that deleting a file instantly erases it; usually only the index entry is removed, which is why secure erasing exists. Another is mixing up bits and bytes: one byte is eight bits. Backing up important files in more than one place protects you against drive failure.
Key ideas
- Cache, RAM, SSD, cloud
- Faster is smaller and pricier
- Bytes, KB, MB, GB, TB
Quick check
Use cases: where Storage and Memory helps
- Homework: review the key idea behind Storage and Memory before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Storage and Memory without notes.
- Visual learning: play with the interactive lab to see how Storage and Memory changes when you adjust its inputs.
- Teaching a friend: explain Storage and Memory in your own words, then compare your version with the key ideas.
Computing ideas run phones, search engines, games and the wider internet.
Frequently asked questions
What is Storage and Memory?
Computers store data in memory hierarchies.
What will I learn in Storage and Memory?
Cache, RAM, SSD, cloud. Faster is smaller and pricier. Bytes, KB, MB, GB, TB.
Is Storage and Memory part of Computer Science?
Yes. It is one of 80 Computer Science topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Storage and Memory lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Storage and Memory?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.