Function pass by reference, return multiple values

This code demonstrates how to use pass-by-reference in C to calculate and return multiple values from a function. Specifically, the areaPerimeter function calculates the area and perimeter of a rectangle based on the provided length and width and updates these values in the caller’s variables by passing their memory addresses (pointers).

#include <stdio.h>

// Function declaration
void areaPerimeter(int length, int width, int *area, int *perimeter);

int main(){

    // Define local variables
    int myLength = 10;
    int myWidth = 5;
    int myArea = 0;
    int myPerimeter = 0;

    // Call the function by passing the length, width
    // and the memory address of area and perimeter variables
    areaPerimeter(myLength, myWidth, &myArea, &myPerimeter);

    // Print results
    printf("Area is: %d\n", myArea);
    printf("Perimeter is: %d\n", myPerimeter);

    return 0;
}

// Function definition
void areaPerimeter(int length, int width, int *area, int *perimeter){
    *area = length * width;
    *perimeter = 2 * (length + width);
}

Explanation of Code

1. Function Declaration

• void areaPerimeter(int length, int width, int *area, int *perimeter);
• The function areaPerimeter accepts two integers (length and width) by value, and two integer pointers (*area and *perimeter) by reference.

2. Main Function

• int myLength = 10; and int myWidth = 5; define the length and width of the rectangle.
• int myArea = 0; and int myPerimeter = 0; initialize variables to store the calculated area and perimeter.
• The function areaPerimeter is called, passing myLength and myWidth by value, while &myArea and &myPerimeter are passed by reference (addresses).
• The function modifies myArea and myPerimeter directly via their pointers.

3. Function Definition

• void areaPerimeter(int length, int width, int *area, int *perimeter) receives length and width as values, while area and perimeter are pointers.
• *area = length * width; calculates the area and assigns it to the memory location pointed to by area.
• *perimeter = 2 * (length + width); calculates the perimeter and assigns it to the memory location pointed to by perimeter.

4. Output

After the function call, myArea and myPerimeter contain the updated values, which are then printed.

Conclusion

This code demonstrates the importance of passing variables by reference in C when a function needs to modify multiple values and return them to the caller. This technique allows efficient memory usage and helps achieve multiple outputs without relying on return values, which is especially useful in C, where functions can only return one value directly. This approach is essential in performance-sensitive applications, as it minimizes the overhead of copying data.