Inside the Machine

A Closer Look at the Code Stream: The Program

At the beginning of this chapter, I defined the code stream as consisting of “an ordered sequence of operations,” and this definition is fine as far as it goes. But in order to dig deeper, we need a more detailed picture of what the code stream is and how it works.

The term operations suggests a series of simple arithmetic operations like addition or subtraction, but the code stream consists of more than just arithmetic operations. Therefore, it would be better to say that the code stream consists of an ordered sequence of instructions. Instructions, generally speaking, are commands that tell the whole computer—not just the ALU, but multiple parts of the machine—exactly what actions to perform. As we’ve ...