OCR J277 | Component 01 | 1.2 Memory and storage | 1.2.1
RAM, ROM and Cache
Quest Briefing
OCR J277 1.2.1 focuses on primary storage. In this quest, you explore the computer's fast-access memory systems and learn how RAM, ROM and cache each support the CPU in different ways.
By the end of this quest, you can...
Stage 2
Learn
Open each concept below to revise the key ideas.
Memory Chamber
The CPU needs fast access to the data and instructions it is using now.
Exam Tip
Do not just say "stores data". Say what kind of data or instructions, whether power is needed, and why the CPU uses it.
Primary storage is memory that the CPU can access quickly while the computer is working. It supports active processing by holding instructions and data that are needed now or very soon.
RAM stores data and instructions currently in use. It is volatile, which means its contents are lost when the computer is switched off. RAM matters because running programs need a fast place to hold active data.
ROM stores start-up instructions needed when the computer begins running. It is non-volatile, so its contents remain when power is off. ROM is normally not changed during everyday use.
Cache is small, very fast memory close to or inside the CPU. It stores frequently used data and instructions so the CPU may wait less often for slower memory access.
Volatile memory loses contents without power. Non-volatile memory keeps contents without power.
Concept Visual
Primary Storage Comparison
RAM, ROM and cache support the CPU in different ways.
Stage 3
Apply
Interactive Apply
Active memory hierarchy
RAM, ROM and cache behaviour ยท Classify examples
- 01Guided
- 02Independent
- 03Diagnose
- 04Mastery
Topic-native Apply mission
Active memory hierarchy
Your role: Evidence investigator. Manipulate the Computer Science model, justify the outcome and complete mastery.
- 01GuidedBoot instructions are stored in ROM.
- 02IndependentCommit to the outcome before it is revealed.
- 03DiagnoseCompare the result with the likely misconception.
- 04MasteryJustify why the system behaved that way.
Active memory hierarchy
RAM, ROM and cache behaviour
Programs, boot instructions and repeated CPU data are routed to the memory type that fits their purpose.
Select and review the relevant evidence before making your judgement.
Boot instructions are stored in ROM.
Volatile working data clears.
Non-volatile ROM still supplies the startup instructions.
- RouteBoot instructions are stored in ROM.
- Power offVolatile working data clears.
- RestartNon-volatile ROM still supplies the startup instructions.
Worked Example
A computer is running a web browser. The browser code and active tabs use RAM while the computer is switched on. Cache may hold frequently used instructions or data close to the CPU so they can be accessed quickly. When the computer is switched off, the contents of RAM are lost.
When the computer is switched back on, ROM is useful because it still contains start-up instructions needed to begin the boot process.
Common Mistakes Tips
Thinking RAM is permanent
RAM is volatile and loses contents when power is off.
Confusing ROM with normal file storage
ROM stores start-up instructions, not everyday user files.
Thinking cache is secondary storage
Cache is small, fast memory used close to the CPU.
Saying stores data too vaguely
Exam answers should explain what kind of data or instructions and why.
Forgetting primary storage is fast access
The CPU needs quick access to active instructions and data.
Stage 4
Exam Practice
Exam-Style Practice
Write, reveal, review
RequiredAnswer in your own words, reveal the model answer, then self-review your confidence.
1. Explain the purpose of RAM.
2. Explain the purpose of ROM.
3. State one difference between RAM and ROM.
4. Explain how cache can improve CPU performance.
5. A student says, "ROM and secondary storage are the same because they both keep data when power is off." Explain why this is not fully correct.
Stage 5
Complete
Quick Check
Question: Why is RAM described as volatile?
Expected answer: Because its contents are lost when the computer is switched off.
Key Terms Recap
Common Mistakes Tips
Thinking RAM is permanent
RAM is volatile and loses contents when power is off.
Confusing ROM with normal file storage
ROM stores start-up instructions, not everyday user files.
Thinking cache is secondary storage
Cache is small, fast memory used close to the CPU.
Saying stores data too vaguely
Exam answers should explain what kind of data or instructions and why.
Forgetting primary storage is fast access
The CPU needs quick access to active instructions and data.