Chapter 6 is the first chapter in the programming layer. In Chapters 2 and 3, we covered the basic information necessary for understanding a computing system, including number systems and ways to represent different types of information in a computer. In Chapters 4 and 5, we covered the hardware components of a computer. Now the emphasis changes from what a computer system is to how it helps us solve problems.

We begin this chapter by looking at machine code, the lowest-level programming language of all—the language that actually runs on the computer’s central processing unit (CPU). We then move up one level to assembly language, a language in which we can use a combination of letters to represent a machine-language instruction. Finally, we introduce the concept of pseudocode as a way to express algorithms.