Understanding C++ references

When we pass values to a function or return values from a function, that is exactly what we are doing – passing/returning by value. What happens is that a copy of the value held by the variable is made and then sent to the function, where it is used.

The significance of this is twofold:

1. If we want the function to make a permanent change to a variable, this system is no good to us.
2. When a copy is made to pass in as an argument or returned from the function, processing power and memory are consumed. For a simple int, or even perhaps a Sprite, this is insignificant. However, for a complex object, perhaps an entire game world (or background), the copying process will seriously affect our game’s performance.

References are the solution to these two problems. A reference is a special type of variable. A reference refers to another variable. Here is an example to help you understand this better:

int numZombies ...