Hello i need some help understanding

[Vrsa]

#include <iostream>
using namespace std;

int main()
{
int x[5];
int i;
for (i = 0; i < 5; i++){
x[i] = i;
}
cout << x[i] << " ";

return 0;
}
// I am wondering why does this code output 5, if x[5] is not defined as 5 , last x[i] = i i think its 4 because of the for loop...

[Ganado]

Hi Vrsa, the issue is your program invokes undefined behavior, so there's no point in trying to make sense of the output itself.

Your array is declared as having a size of 5.
This means it has 5 slots for numbers to be assigned to.
x[0], x[1], x[2], x[3], and x[4] are valid elements to access. Notice that it starts at 0, not 1.

After the for loop, your i variable still exists and is set to the value 5.
The element at x[5] doesn't exist. You should not try to access it.

You can avoid this problem by limiting the i variable to the scope of the for loop.

#include <iostream>
using namespace std;

int main()
{
    int x[5];
    for (int i = 0; i < 5; i++){
        x[i] = i;
    }
    cout << x[i] << " "; // COMPILER ERROR: i is not defined in this scope

    return 0;
}