Difference between parameters and arguments in a function

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When I first started learning how to program (in Java) using a book from my local library, they would always mention "parameters" and "arguments", but I never quite understood the difference.

Some of you as programmers may have wondered at some point, what is the difference between a parameter and an argument in a function?

Let's take a look at a the difference:

• When declaring a function the data it takes (usually goes inside parentheses in most programming languages) is called parameters.

• When invoking (calling) a function the data we pass to it is referred to as arguments.

We are going to use a code example in C to make things more clear:

1  #include <stdio.h>
2 
3  int addTwoNumbers(int x, int y) {
4     int sum = x + y;
5
6     return sum;
7  }
8
9  int main(void) {
10    int a = 5;
11    int b = 7;
12    
13    int c = addTwoNumbers(a, b)
14
15    printf("The sum of the two numbers is: %d\n");
16 
17    return 0;
18 }

• On line 3 of the code block we declared a function called addTwoNumbers, the parameters it takes are two int type variables named x and y:

3  addTwoNumbers(int x, int y)

• We invoke the addTwoNumbers function on line 13, and we pass the a and b variables as arguments:

13 addTwoNumbers(a, b)