CPU Architecture

Computer ScienceOCRGCSEUnit: 3.4 Computer Systems
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The basics

The Restaurant Kitchen

The Restaurant Kitchen

Imagine you're the head chef in a busy restaurant kitchen. You (the Control Unit) read orders from the waiters (instructions from memory), tell your sous chefs (the ALU) exactly what to cook, and use the counter space (the Registers) to temporarily hold ingredients while preparing dishes. The pass-through window and kitchen intercom (the Buses) connect you to the dining room and storage areas. Just as nothing gets cooked without you coordinating every step, nothing happens in a computer without the CPU orchestrating every single operation - billions of times per second!
What does CPU stand for?: Central Processing Unit
Key terms

Computer Science glossary

What does CPU stand for?
Central Processing Unit
What does ALU stand for?
Arithmetic Logic Unit
Spotlight
Deep Dive: Von Neumann Architecture

Modern computers follow the Von Neumann architecture, designed in the 1940s. The key idea: both the program instructions AND the data they work on are stored in the SAME memory. Think of a chef who must read the recipe from the same counter where they're preparing ingredients - they can only do ONE thing at a time.

Exam tip

Earn the mark scheme marks

Exam Tips - The CPU

When asked "Describe the CPU" always mention ALL THREE parts:

  • Control Unit - fetches, decodes, sends control signals
  • ALU - arithmetic AND logic operations
  • Registers - fast temporary storage inside CPU

Common mistakes to avoid:

  • Saying "ALU does calculations" - say "arithmetic AND logic operations"
  • Forgetting the Control Unit sends control signals
  • Confusing buses - Address is WHERE, Data is WHAT
  • Saying registers store data "permanently" - they're TEMPORARY

Now try it yourself

Quiz · Question 1 of 16

Which component of the CPU carries out arithmetic and logical operations?

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