Function parameters are variables declared in a function’s parameter list. They receive the values supplied through arguments when the function is called.

#include <stdio.h>

int multiply(int a, int b)
{
    return a * b;
}

int main(void)
{
    int result1 = multiply(4, 5);
    int result2 = multiply(6, 3);

    printf("%d\n", result1);
    printf("%d\n", result2);

    return 0;
}

Example Output #

20
18

Explanation #

The function definition declares two parameters:

int multiply(int a, int b)

Here, a and b are parameters of type int. Each call supplies two argument values.

multiply(4, 5);
multiply(6, 3);

During the first call, a receives 4 and b receives 5. During the second call, a receives 6 and b receives 3.

Parameters and Arguments #

Functions with Different Parameter Lists #

A function can accept multiple parameters of different types:

double calculateArea(double length, double width)
{
    return length * width;
}

It can also accept no parameters:

void display(void)
{
    printf("Ready\n");
}

In a function definition, void inside the parentheses explicitly indicates that the function accepts no parameters.

The number and types of arguments must be compatible with the function’s declared parameter types. C passes argument values to parameters; it does not automatically provide reference-style parameter passing.