*C programming output*

Question

#include<stdio.h>
void foo(int, int);
void main()
{
int a=2048; sum=0;
foo(a, sum)
printf("%d\n", sum);
}
void foo(int n, int sum)
{
int k=0, j=0;
if(n ==0) return;
k =n%10;
j=n/10;
sum=sum+k;
foo(j,sum);
printf("%d", k);
}

please explain the answer and meaning of statement :- return 0;

Answer 1

#include<stdio.h>
void foo(int, int);
void main()
{
int a=2048;
int sum=0;
foo(a, sum);
printf("%d\n", sum);
}
void foo(int n, int sum)
{
int k=0, j=0;
if(n ==0) return;
k =n%10;
j=n/10;
sum=sum+k;
foo(j,sum);
printf("%d", k);
}