Hardware is the physical parts of a computer. This mini-lesson covers the CPU and von Neumann architecture, registers, the fetch-decode-execute cycle, RAM & ROM, cores, cache and clock speed, input/output devices, sensors, and storage (magnetic, optical, solid state).
Work through each screen, answer the questions, and collect ⭐ stars. Press Start when ready.
CPU & von Neumann architecture
The CPU & von Neumann
The CPU (Central Processing Unit) processes data and instructions. In the von Neumann architecture, both data and instructions are stored together in the same memory. Key components:
Control Unit (CU) — decodes instructions and sends control signals to coordinate the CPU.
Arithmetic Logic Unit (ALU) — does the calculations and logic comparisons.
Registers — tiny, very fast stores inside the CPU, such as the MAR, MDR, PC (Program Counter) and ACC (Accumulator).
Buses — wires that carry data, addresses and control signals between parts.
Quick check
Which part does the maths?
?Which part of the CPU carries out calculations and logical comparisons?
Fetch-decode-execute cycle
The fetch-decode-execute cycle
The CPU runs a program by repeating a three-step cycle for every instruction:
Repeat forever: fetch the next instruction, decode it, execute it.
Fetch — the next instruction is copied from memory into the CPU (the PC holds its address).
Decode — the Control Unit works out what the instruction means.
Execute — the CPU carries it out (e.g. the ALU does a calculation).
Quick check
Order of the cycle
?What is the correct order of the three stages the CPU repeats?
RAM & ROM
RAM & ROM
RAM (Random Access Memory) — volatile (contents lost when power is off); holds the programs and data currently in use; can be read and written; its contents change constantly.
ROM (Read Only Memory) — non-volatile (keeps contents without power); stores start-up instructions like the BIOS/bootstrap; normally read only.
Don’t confuse: RAM is not the same as storage (like an SSD). RAM is temporary working memory; adding more RAM lets more programs run smoothly at once.
Sort it
RAM, ROM or optical?
Tap a statement, then tap the group it belongs to.
⚡ RAM
🔒 ROM
💿 Optical
Cores, cache & clock speed
What makes a CPU faster?
Clock speed — measured in GHz; how many cycles per second. Higher clock speed → more instructions per second.
Number of cores — each core can process instructions; more cores let the CPU do more tasks in parallel.
Cache — a small amount of very fast memory inside/near the CPU that stores frequently used data and instructions, so the CPU waits less. A larger cache generally improves performance.
Match it
Match the term to its meaning
Tap a description on the left, then its matching term on the right.
Description
Term
Input, output & sensors
Input, output & sensors
Input devices send data into the computer (keyboard, mouse, microphone, scanner, camera). Output devices send results out to the user (monitor, printer, speaker, actuator).
Sensors are input devices that measure a physical quantity continuously — e.g. temperature, light, pressure, moisture, motion/infra-red, pH. They give data to control and monitoring systems (an analogue reading is converted to digital for the computer).
Quick check
Input or output?
?Which of these is an output device?
Secondary storage
Magnetic, optical & solid-state storage
Secondary storage keeps data permanently (non-volatile). Three types:
Magnetic (e.g. HDD, magnetic tape) — data stored as magnetised patterns on spinning platters. High capacity, low cost, but has moving parts.
Optical (CD, DVD, Blu-ray) — data stored as pits and lands read by a laser. Cheap and portable, lower capacity.
Solid state (SSD, USB flash drive, memory card) — uses flash memory with no moving parts. Fast, robust and low-power, but usually more expensive per GB.
Quick check
Which storage?
?A designer wants fast, robust storage with no moving parts for a laptop. Which type is most suitable?
Quick check
Volatile memory
?Which statement about RAM is correct?
Quick check
Sensors
?In a greenhouse control system, which device would measure how damp the soil is?
Recap
The big ideas to know
CPU: Control Unit + ALU + registers; von Neumann stores data & instructions together
Cycle: fetch → decode → execute (repeat)
RAM = volatile working memory · ROM = non-volatile start-up store