A function can return a computed value to its caller using the return statement. When multiple values need to be provided, a function can return a structure, or write results into caller-provided objects through pointers.

#include <stdio.h>

int calculateSum(int a, int b)
{
    return a + b;
}

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

int main(void)
{
    int sum = calculateSum(10, 20);
    double area = calculateArea(5.0, 3.0);

    printf("Sum = %d\n", sum);
    printf("Area = %.2f\n", area);

    return 0;
}

Example Output #

Sum = 30
Area = 15.00

Explanation #

The function calculateSum() returns an integer:

return a + b;

The calling code receives the value and stores it in sum.

The function calculateArea() returns a double:

return length * width;

Its return value is stored in area.

Ways to Return Data #

A function cannot return an array type directly in C. To return array-related data, use a pointer to valid storage, a structure containing an array, or a caller-provided output array. The lifetime of the underlying storage must be considered when returning pointers.