Computer Systems and Hardware
Domain focus
Computer Systems and Hardware tests component identification, the fetch–decode–execute cycle, memory and storage differences, and how specifications affect performance. Expect questions that ask why a computer is slow or which device is input, output or both.
Core rules and concepts
- The CPU has the ALU (arithmetic and logic), control unit (coordinates), registers (fast temporary storage) and cache. It repeats fetch, decode, execute, store.
- RAM is volatile working memory; ROM is non-volatile firmware storage; cache is faster and smaller than RAM.
- Storage (HDD, SSD, optical, flash) is non-volatile. SSDs have no moving parts and faster random access than HDDs.
- Input devices capture data (keyboard, scanner, sensor); output devices present results (monitor, printer); touchscreens are both.
- Performance depends on clock speed, cores, cache size, RAM size, storage type and bus speed, not one number alone.
Worked example
Laptop A: 4 cores at 2.4 GHz, 8 GB RAM, HDD. Laptop B: 4 cores at 2.4 GHz, 16 GB RAM, SSD. For opening many browser tabs and editing large images, B is likely faster: more RAM reduces disk swapping, and the SSD lowers load times. For a single simple word-processing task, the difference may be small because both CPUs are similar. The reasoning is to match the bottleneck to the component, not to assume “bigger is always faster”.
Traps that cost marks
Saying RAM stores files permanently; confusing RAM with ROM; calling a monitor an input device; assuming a higher clock speed always beats more cores; ignoring that a fast CPU is limited by slow storage or too little RAM; and forgetting that a printer is output while a scanner is input.