PyGCSE Python Lab

The CPU and Fetch-Decode-Execute Cycle

Learn about CPU architecture, registers, buses, and how the fetch-decode-execute cycle works.

📚 Learning Steps

💡 Study Tips
  • • Read through at your own pace
  • • Try the interactive simulators hands-on
  • • Study the pseudocode — it appears in exams
  • • Quiz yourself before moving on

Step 1: What is the CPU?

📖 Theory

The CPU (Central Processing Unit) is the brain of the computer. It processes all instructions and performs calculations.

The CPU contains three main components:

1. ALU (Arithmetic Logic Unit) — performs calculations and logical comparisons
2. CU (Control Unit) — manages the flow of data and instructions, sends control signals
3. Registers — tiny, ultra-fast memory locations inside the CPU for temporary storage

The CPU can only process one instruction at a time (per core), but it does this billions of times per second.

🎯 Key Points
  • CPU = Central Processing Unit (the processor)
  • ALU performs arithmetic (+, -, ×, ÷) and logic (AND, OR, >, <)
  • CU controls the sequence of operations and sends signals
  • Registers are small, fast storage inside the CPU
0/7 steps completed