This chapter focuses on the code and how to structure it. Programs are a series of instructions given to computers to execute. A key point in this definition is the combination of “series” and “execute.” By default, programs run step by step, or instruction by instruction, from start to end. This is a fundamental concept in programming, commonly referred to as sequential execution. This chapter reviews common methods of controlling the program flow. It starts with the simple, old, and infamous GoTo statement, showing why it was not a good way of managing the flow of a program. Then, it discusses selection and iteration as two of the most basic control flow mechanisms in modern languages. Together with modularization, they are the basis of what we call Structured Programming.