Passing a copy of a variable

When a program passes a variable as a parameter to a function by value

• A copy of the contents of the variable is made
• The copy is passed to the function as a parameter

The function can do just about anything that it wants to do with the incoming parameter.

Cannot modify the original variable

However, the one thing that it cannot do with the parameter is to modify the contents of the original variable.

If it modifies the value of the parameter, it simply modifies the copy and doesn't modify the value of the original variable.