Computer Systems and Hardware
What you must know
A computer system is hardware plus software working together. Learn the roles of the CPU (control unit, ALU, registers, clock speed, cores), main memory (RAM volatile, ROM non-volatile), secondary storage (magnetic, optical, solid-state), input and output devices, and the buses that carry data, addresses and control signals. Understand the fetch–decode–execute cycle and how cache and registers speed it up.
Traps candidates fall into
- Confusing RAM with ROM: RAM is volatile and loses contents on power-off; ROM keeps data and is used for firmware such as the BIOS.
- Mixing up input and output: a touchscreen is both; a printer is output only.
- Assuming more GHz always means faster: cores, cache size and bus width also matter.
- Forgetting that solid-state storage has no moving parts, so it is faster and more shock-resistant than a hard disk.
- Describing the CPU as storing programs permanently - that is secondary storage's job.
Rule of thumb
Match each device to its job using the input–process–output model: if data enters the computer it is input; if it leaves it is output; if it holds data when power is off it is secondary storage.
Worked example
A school wants a laptop for video editing. More RAM helps hold large files in memory, a faster multi-core CPU speeds rendering, an SSD reduces loading time, and a dedicated GPU handles graphics. Justify each choice by linking the component to the task - never list parts without a reason.