Explain me this code

Question

#include <iostream>
using namespace std;
int sum = 0;
int recSum(int n) {
//complete the function
if (n <= 1) {
sum += 1;
} else {
for (int x = 1; x <= n;) {
sum = sum + n;
n--;
}
}
}

int main() {
//getting input
int n;
cin >> n;

//call the recursive function and print returned value
recSum(n);
cout << sum;
return 0;
}

Answer 1

First of all the code is not well-written. Since your function aren't returning anything, why don't you use the void instead of using int type?
Now, let me explain what does the code does.
I believe the code works like that,
input:5
output:
5+4+3+2+1=15
If the value of n is less than or equal 1 the value of sum increments 1 and it prints 1.Otherwise if the value of n is greater than 1 it goes to the else statement of that function.
Then this line works,
for (int x = 1; x <= n;) {
sum = sum + n;
n--;
}
I must say this is another bad way of writing code because you can use for (int x = 1; x <= n;n--) instead of adding n-- at the end or you can use x++ and use :
sum=sum+x; instead of sum=sum+n;
Anyway, the code starts from adding the value of n first and then decrements and adding again and again until n becomes <1;
So if you give the input 5, your code will Start adding from 5 then 4 then 3... until the value of n is less than 1 and since the sum is a global variable it can be called from the main function. So the value of sum becomes: 5+4+3+2+1=15

Answer 2

It's look like, coder was tring combine for loop and recursion. And Its bad idea. He must first decide what method he want to use.

a) using for loop:

Int sum=0;
For (int i = 0; i< n; i++)
{
Sum += i;
}
Return sum;

B) using recursion:

If(n==1) return 1;
Else return n+recSum(n-1);

But because name of the funkcion is recSum, I thing the gol is practise recursion, whitch mean optiin B.