At the beginning of this chapter, we saw that a function can take input parameters. Before we delve into all possible type of parameters, let's make sure you have a clear understanding of what passing a parameter to a function means. There are three key points to keep in mind:

• Argument-passing is nothing more than assigning an object to a local variable name
• Assigning an object to an argument name inside a function doesn't affect the caller
• Changing a mutable object argument in a function affects the caller

Let's look at an example for each of these points.