The functions illustrated in this lesson are all global functions.
Global functions are defined outside of a class and are accessible by any code in the program that knows the name of the function.
Global functions are not allowed in newer OOP languages such as Java and C#.
(They are called methods instead of functions in Java and C#.)
Functions or methods can be defined inside of classes in C++, Java, and C#.
Useful for future learning
Therefore, what you have learned in this lesson is generally applicable to the use of functions or methods that are defined inside of classes.