Function Parameter

There are two types of arguments/parameters

• Actual parameters
• Formal parameters

Actual parameters :

Are parameters that appear in function calls.

Syntax :

Function_name(actual parameters)

Formal parameters :

Are parameters that appear in function declarations.

Syntax :

return_type function_name(formal parameters)

Example of actual parameter and formal parameter :

    #include <stdio.h>

    /* function declaration */
    int sum(int num1, int num2);

    int main ()
    {
    /* local variable definition */
    int a = 10;
    int b = 20;
    int s;

    /* calling a function to get sum of the numbers */
    s = sum(a, b); //Actual Parameter

    printf( "Sum of the numbers is : %d\n", s);

    return 0;
    }

    /* function returning the sum of the two numbers */
    int sum(int num1, int num2) //Formal Parameter
    {
    /* local variable declaration */
    int result;
    result = num1 + num2;
    return result;
    }

Output :

Sum of the numbers is : 30

Explanation :

In calling function - sum(a,b), a and b are actual parameters.
And parameters in function definition - int sum(int num1, int num2), num1 and num2 are formal parameters.

NOTE :

• Formal parameters are always variables.
• Actual parameters need not have to be variables. You can use variables, numbers, expressions, or even function calls as actual parameters.