how to do recursion in c code example

Example 1: recursion questions in c

#include <stdio.h>
int sum(int n);

int main() {
    int number, result;

    printf("Enter a positive integer: ");
    scanf("%d", &number);

    result = sum(number);

    printf("sum = %d", result);
    return 0;
}

int sum(int n) {
    if (n != 0)
        // sum() function calls itself
        return n + sum(n-1); 
    else
        return n;
}

Example 2: recursion questions in c

#include <stdio.h>

int fibonacci(int i) {

   if(i == 0) {
      return 0;
   }
	
   if(i == 1) {
      return 1;
   }
   return fibonacci(i-1) + fibonacci(i-2);
}

int  main() {

   int i;
	
   for (i = 0; i < 10; i++) {
      printf("%d\t\n", fibonacci(i));
   }
	
   return 0;
}