Please why is the output 30.

Question

#
<iostream>
using namespace std;

int main()
{
int i=6;

for (i;i<=9;++i) {}
cout << 3*i << endl;

return 0;
}

Answer 1

Last iteration, i = 9

i<=9 == true so i receives an increment and is equal to 10

3 * 10 = 30

Answer 2

Ok, thank you very much

Answer 3

Comparing the examples

for (i;i<=9;++i) {} <--- You see the empty brackets?
cout << 3*i << endl;

Thats because it's checking the conditional and incrementing the iterator without executing additional code each iteration. After it finishes looping it only prints i value once.

for (i;i<=9;++i)
{
cout << 3*i << endl;
}

This one it prints 3 * i every iteration.

Answer 4

#
<iostream>
using namespace std;

int main()
{
int i=6;

for (i;i<=9;++i)
{
cout << 3*i << endl;
}
return 0;
}

What does this code give me an answer of 18,21,24,27, what is the main difference between these two codes.