A statement in C is a complete unit of execution terminated with a semicolon. A statement can be as simple as a unit of execution like int a = 100; or printf(“Hello World!”);. Statements inside of the main function are executed in a top-down order. What if you want to change the order of how statements are executed, or even prevent statements from being executing based on a certain condition? C provides a set of control flow statements to perform that very task. The most basic of the control flow statements is the if statement.