In the previous chapter, you learned about the uses of variables, different data types, and functions. You created your own function and learned how to get basic information from a user with the raw_input() function. Using these building blocks, you can begin to design basic programs.
The first program we make will be a five-function calculator that calculates two numbers as input. The calculator will help us learn to understand the mathematical functions that are a part of Python, which will be useful for our game at the end of the book. In addition to this, this calculator will form the foundation for a more complex calculator in Chapter 5, Loops and Logic.