PyGCSE Python Lab

CUALUR CPU & FDE Cycle Simulator

Explore the Von Neumann architecture, the Fetch-Decode-Execute cycle, and trace through a real program step by step. OCR J277 §1.1.1.

📖 Learn CPU & FDE Cycle

Von Neumann Architecture

Click on components to highlight them. Instructions and data are stored in the same memory.

🧠 Key Registers

  • PC (Program Counter) — holds address of next instruction
  • MAR (Memory Address Register) — holds address being read/written
  • MDR (Memory Data Register) — holds data being transferred
  • ACC (Accumulator) — holds results of calculations
  • CIR (Current Instruction Register) — holds instruction being decoded

🔌 Buses

  • Address Bus — carries memory addresses (one-way: CPU → memory)
  • Data Bus — carries data/instructions (two-way)
  • Control Bus — carries control signals (read/write, clock, etc.)