This lesson explains how a computer's central processing unit is built and how it runs a program. You will learn the von Neumann model, the job of each register and bus, and the step-by-step fetch-decode-execute cycle.
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Von Neumann architecture
The von Neumann architecture is a design in which both program instructions and data are stored together in the same main memory.
The central processing unit fetches instructions one at a time from memory, decodes them and then executes them.
Because instructions and data share the same memory and the same bus, they cannot be moved at the same instant, so they take turns.
This stored-program concept is the basis of almost all modern general-purpose computers.
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1. Which statement best describes the key feature of the von Neumann architecture?
2. What is the purpose of the Program Counter (PC)?
3. Which bus is unidirectional, carrying memory addresses in one direction only?
4. During the fetch stage, the address in the Program Counter is first copied into which register?