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How does a CPU work?
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Quick answer
A CPU works by fetching instructions from memory, decoding what each one means, and executing it — billions of times a second. It repeats this fetch-decode-execute cycle on simple operations like add, compare, and move data that together run every program on your device.
Step by step
- It runs a constant 'fetch-decode-execute' cycle: get an instruction, work out what it means, carry it out.
- A clock keeps everything in step, ticking billions of times per second (gigahertz).
- It only does simple operations — arithmetic, comparisons, moving data — but at staggering speed.
- Multiple 'cores' let it run several streams of instructions at once.
- On-chip memory called cache keeps frequently used data close, so the CPU isn't left waiting on slower main memory.
People also ask
What does clock speed (GHz) mean?
It is how many cycles the CPU runs per second — 3 GHz is three billion cycles a second. More cycles can mean more work, though design and core count matter just as much.
What is the difference between a CPU and a GPU?
A CPU has a few powerful cores great at varied, sequential tasks; a GPU has thousands of simpler cores built to do the same operation on lots of data at once.
What are cores?
Each core is an independent processing unit. More cores let the CPU handle multiple tasks or threads truly in parallel.