In this chapter, we presented the computer’s architecture, focusing on its processor (CPU) design and implementation in order to understand how it runs a program. Today’s modern processors are based on the von Neumann architecture, which defines a stored-program, universal computer. The general-purpose design of the von Neumann architecture allows it to execute any type of program.

To understand how the CPU executes program instructions, we built an example CPU, starting with basic logic-gate building blocks to create circuits that together implement a digital processor. A digital processor’s functionality is built by combining control, storage, and arithmetic/logic circuits, and is run by a clock circuit that drives the Fetch, Decode, Execute, and WriteBack phases of its execution of program instructions.

All processor architectures implement an instruction set architecture (ISA) that defines the set of CPU instructions, the set of CPU registers, and the effects of executing instructions on the state of the processor. There are many different ISAs, and there are often different microprocessor implementations of a given ISA. Today’s microprocessors also use a variety of techniques to improve processor performance, including pipelined execution, instruction-level parallelism, and multicore design.

For more breadth and depth of coverage on computer architecture, we recommend reading a computer architecture textbook¹.