What is the use of `return(0)` in C? I have written programs which work fine without using it. Please explain it to me in a simplified manner, since I'm a beginner in C. If the answer is complex it might confuse me even more...

```
#include <stdio.h>
#include <stdlib.h>

int main()
{
    float km, meter, feet, inch, cm;
    printf("Enter the distance(must be in km: \n");
    scanf("%f", &km);
    cm = 100000*km;
    inch = 39370.1*km;
    meter = 1000*km;
    printf("The distance between the cities in cm is %f \n", cm);
    printf("The distance between the cities in inches is %f \n", inch);
    printf("The distance between the cities in meters is %f \n", meter);
}

```