Why would this code give an error?

Question

Got this question in a quiz, it was created by a user. It goes as followed :

What is the output of this code?
#include <iostream>
using namespace std;
int main(){
for (int i =0, i <7, i++){}
cout<<i;

I thought the correct answer would be 7? But i was wrong, the code would result in an error. Can anyone explain why? I think it was a syntax error?

Answer 1

Variable "i" only 'exists' within the for loop. When trying to call it outside of the loop this message appears.

..\Playground\:6:7: error: 'i' was not declared in this scope
cout<<i;
^

Answer 2

Lookup variable scope in C.