Control Flow

Abstract

The programs listed in the previous chapter were architecturally simple because they were straight line programs. That is, statements were executed in the order in which they appeared without any branching or repetition. Most programming problems are not so simple. In fact, the great power of programming languages stems from their ability to instruct the computer to perform the same task repeatedly, or to perform a different task if parameters change. In high-level programming languages, this is accomplished with control flow statements that allow you to alter the sequential flow. Control flow statements fall into two general categories: conditional branching and looping. Conditional branching is the ability to decide whether or not to execute code based on the value of an expression. Looping, also called iteration, is the ability to perform the same set of operations repeatedly until a special condition is met.

“Begin at the beginning,” the King said, very gravely, “and go on till you come to the end: then stop.”

Lewis Carroll, Alice in Wonderland