My problem about while loop!

Question

int main() {
int num = -2;
int number;
int total = 0;
while (num <= 5) {
cin >> number;
total+=number;
num=num+1;
}
cout << total << endl;
What do total+=number; and num+1; work? How does num+1; work??

Answer 1

Thanks a lot fella👍

Answer 2

total+=number is another way of saying “add “number” to total”. It can also be written as “total=total+number”. The line “num=num+1” is similar, you are adding 1 to “num”, which can also be written as “num+=1” or even “num++”. This will increment “num” until num is equal to 5, then afterwards, your console will print the total.

Answer 3

I think you got me wrong.. I mean what's the point of them ? What will happen if I leave them off deliberately ? And what will happen if I write num=num+2:

Answer 4

If you leave “num=num+1” out of the loop, num will never increase, and always equal -2. If you leave out “total+=number”, then your cout line will print total as 0 since it was initialized as 0 and never changed. If you write “num+=2” instead, num will reach 5 in the while loop more quickly.

Answer 5

Thank you . Just one more questio.. how does num=num+1; work?? What is the reason of result of choosing another number instead of 1 , for num=num+1;

Answer 6

So num is initialized as -2. When you add 1 (num=num+1), num then becomes -1, then 0, then 1, and adds one until num is equal to 5 (as defined in your while loop). This means your loop will run 7 times (-2 through 5 is a difference of 7). If you add 2 to num each time instead of 1, num will go from -2 to 0, then 2, then 4, and then stop. It wouldn’t add 2 to num after 4 since the while loop only runs while num is less than or equal to 5 (and if you added 2 to 4, the result “6” is greater than five, so it stops at 4).

So to paraphrase, num=num+1 makes the loop run 7 times, but num=num+2 makes the loop run only 3 times.