代码工作正常，但我不明白它显示的内容

Question

So I'm reading C++ Primer (5th edition) and this is the example code they give to explain the while statement:

#include <iostream>
int main()
{
    int sum = 0, val = 1;
    // keep executing the while as long as val is less than or equal to 10
    while (val <=10) {
        sum += val; // assigns sum + val to sum
        ++val; // add 1 to val
    }
    std::cout << "Sum of 1 to 10 inclusive is " << sum << std::endl;
    return 0;
}

And this is the program in the Command Line prompt:

I just can't understand where the 55 came from..

Isn't it supposed to be:

sum = 0
var = 1
sum = 0 + 1
var = 1 + 1
-snip-
sum = 6
var = 4

So shouldn't it print 6? I'm really confused.

Answer 1

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55

Answer 2

What it does is:

1. initializes val to 1

2. increments val till it reaches 10 in each iteration

3. this val is added to sum in each iteration

4. after 10 iterations, this sums up to 55.

Still not clear, use a debugger and check each step.