Memory is one of the most frequently tested topics in IB Computer Science, yet many students lose marks by giving vague or incomplete explanations. In IB exams, students are expected to clearly distinguish between RAM, ROM, and cache memory, explaining not only what they are but why they exist and how they affect performance.
Understanding memory types also helps students make sense of CPU speed, system efficiency, and the fetch–decode–execute cycle.
What Is RAM?
Random Access Memory (RAM) is the computer’s main working memory.
RAM is used to:
- Store programs currently running
- Store data being actively used
- Hold instructions waiting to be executed
Key characteristics of RAM:
- Volatile: data is lost when the computer is turned off
- Fast: much faster than secondary storage
- Read/write: data can be changed constantly
In IB exam questions, RAM is often linked to:
- Program execution
- Multitasking
- System performance
More RAM allows more programs and data to be accessed at the same time.
What Is ROM?
Read Only Memory (ROM) stores permanent instructions needed to start the computer.
ROM is used for:
- Boot-up instructions
- Firmware
- Low-level system control
Key characteristics of ROM:
- Non-volatile: data is not lost when power is off
- Read-only (in most cases)
- Stores essential startup instructions
In IB Computer Science, ROM is commonly linked to:
- The boot process
- Loading the operating system
- System stability
Students often lose marks by saying ROM stores “files” or “programs” — it stores startup instructions, not user data.
What Is Cache Memory?
Cache memory is a small amount of extremely fast memory located close to or inside the CPU.
Cache is used to:
- Store frequently accessed data
- Reduce access time to RAM
- Improve overall CPU performance
Key characteristics of cache:
- Much faster than RAM
- Much smaller than RAM
- Expensive compared to other memory types
Cache works by predicting what data the CPU will need next and storing it nearby.
Why Cache Is Needed
Without cache:
- The CPU would constantly wait for RAM
- Processing speed would drop significantly
Cache reduces this delay by:
- Storing recently used instructions
- Keeping frequently accessed data close to the CPU
This is especially important in modern, high-speed processors.
Comparing RAM, ROM, and Cache
In IB exams, students must be able to compare memory types clearly:
- RAM: working memory for active programs
- ROM: permanent memory for startup
- Cache: high-speed memory to improve performance
Each has a specific role, and none replace the others.
Common Student Mistakes
Students often:
- Confuse RAM and cache
- Say ROM stores user data
- Forget volatility
- Ignore performance differences
Precise comparisons are essential for full marks.
Final Thoughts
RAM, ROM, and cache exist because computers need different types of memory for different purposes. RAM supports active processing, ROM ensures the system can start, and cache keeps the CPU running efficiently.
Understanding these differences gives students a strong foundation for performance, CPU architecture, and exam success in IB Computer Science.
