In this lesson, you learned how to create and use playground files, which allow you to explore and experiment with Swift. The more you explore and experiment, the more you will learn. You saw how Swift implements data types, and how to use constants and variables to store numbers, words, and logic statements in your program. You also learned about type inference, type annotation, and type safety, which help you to write code concisely and with fewer errors. You looked at how to perform operations on numbers and strings, how to fix errors, and how to print to the Debug area to help you understand how your program works.

At this point, you can now write simple programs that process letters and numbers. You now know how to create and save playgrounds, the different data types, how to create and use variables and constants, how to use type inference to assign variable types, and how to perform common operations. Good job!

In the next chapter, you'll look at options and conditionals. Options deal with cases where a variable may or may not have a value, and conditionals deal with branching in your program.