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RAM holds working programs and data and is usually volatile: contents are lost when power is removed. ROM stores persistent instructions such as boot-related code in the school model. Cache is smaller fast memory near the processor. Secondary storage preserves files long term. Virtual memory uses secondary storage to support a larger working-memory demand, but is slower than RAM and does not create additional physical RAM.
Video by Craig'n'Dave. The video’s own board label is retained; follow the specification reference and scope notes on this lesson for assessed content.
Viewing focus: Compare RAM, ROM, cache and secondary storage
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: Which is usually volatile?
RAM. Working-memory contents usually disappear without power.
After watching 2: How many bits form one byte?
Eight. This conversion is independent of decimal or binary capacity prefixes.
What you'll be able to do
RAM holds working programs and data and is usually volatile: contents are lost when power is removed. ROM stores persistent instructions such as boot-related code in the school model. Cache is smaller fast memory near the processor. Secondary storage preserves files long term. Virtual memory uses secondary storage to support a larger working-memory demand, but is slower than RAM and does not create additional physical RAM.
A bit is a binary digit and a byte contains eight bits. Capacity prefixes can follow decimal or binary conventions; use the convention stated in the question. Do not silently treat 1 kB as both 1000 and 1024 bytes in one calculation. Convert bits to bytes before comparing a bit-rate with a file size in bytes. Metadata, formatting and overhead may make real usable capacity differ from a simple raw calculation.
Magnetic disks offer large capacities at useful cost, solid-state storage has no moving mechanical parts and often provides fast access, and optical media may support distribution or archival uses. Compare capacity, speed, durability, portability, cost and intended conditions. A storage recommendation should connect two or more properties to the scenario. The largest capacity is not automatically best for a small embedded device or a portable sensor.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: A portable recorder will be shaken while operating. Why might solid-state storage suit it?
Durability and access characteristics suit the scenario, subject to capacity and cost.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.