Hardware: CPU, Memory, Input/Output and Storage
Domain focus
Hardware questions test the CPU fetch–decode–execute cycle, memory types, input/output devices and storage, and the ability to choose suitable devices for a stated situation.
Core rules
- CPU: the arithmetic logic unit (ALU) does arithmetic and logic; the control unit (CU) coordinates; registers hold current data and addresses - program counter, instruction register, memory address register, memory data register and accumulator.
- Cycle: fetch the instruction, decode it, execute it and store the result.
- Memory: RAM is volatile and holds current programs/data; ROM is non-volatile and stores firmware; cache is small, fast memory between CPU and RAM. Units: 8 bits = 1 byte; 1024 bytes = 1 KB; 1024 KB = 1 MB; 1024 MB = 1 GB; 1024 GB = 1 TB.
- Input: keyboard, mouse, scanner, microphone, sensors, touchscreen. Output: monitor, printer, plotter, speaker. Storage: magnetic HDD, optical CD/DVD, solid-state SSD/USB. Primary storage is directly accessed by the CPU; secondary storage is permanent.
Worked example
A PC has 4 GB RAM and a 1 TB HDD. Explain why upgrading to 8 GB RAM can speed up multitasking but does not increase permanent storage. Reasoning: RAM holds the programs and data currently in use; more RAM lets more applications stay in memory and reduces slow swapping to disk. The HDD remains the non-volatile store, so its 1 TB capacity is unchanged. The answer must link RAM to active work and HDD to permanent storage.
Traps
- Saying RAM keeps files permanently.
- Confusing cache with main memory.
- Treating an SSD as magnetic; it uses flash memory.
- Naming a monitor as input because it is a touchscreen - only the touch layer is input.
- Using 1000 instead of 1024 in binary storage conversions.