In the last chapter, you looked at data types, constants and variables, and operations. At this point, you are able to write simple programs that process letters and numbers. However, in many cases, programs are not linear, which is to say they don't always proceed in sequence. Oftentimes, you will need to execute different instructions based on a condition. Swift allows you to do this by using conditionals, and you will learn how to use them in this chapter.
Another thing you may have noticed is that, in the last chapter, each variable or constant was immediately assigned a value. What if you require a variable where the value may not be present initially? You will need a way to create a variable that may or may not have a value. Swift allows you to do this by using optionals, and you will also learn about them in this chapter.
By the end of this...
