What does this simple code mean?

[laurisplus]

What does this code mean? Why do I get particular numbers when running it?

  #include "stdafx.h"
#include <iostream>
using namespace std;

int main(){
	int a, s = 0;
	cin >> a;
	for (int i = 1; i <= a; i++) s += i;
	cout << s << endl;

	system("pause");
}

[booradley60]

This is how descriptive variable names can help. The code below is the same (other than the more descriptive output), but just by reading it you probably have a better idea of what it is doing.

#include "stdafx.h"
#include <iostream>
using namespace std;

int main()
{
    int limit, sum = 0;
    cin >> limit;
    for (int i = 1; i <= limit; i++) sum += i;
    cout << "The sum of numbers from 1 to " << limit << " is " << sum << endl;

    system("pause");
}

[laurisplus]

Thank you very much!