Why does my simple calculator always answer as 8?

Question

I just started learning a few hours ago, so bear with me. I wrote it as follows
#include <iostream>
using namespace std;

int main ()
{
int a;
int b;
int c = a+b;
cin >> a;
cin >> b;
cout << c;
return 0;
}

No matter what I input or don't input into the variables when it asks, it always answers "8". I'm very confused.

Answer 1

Hi Kirby, a couple of simple rules.
When initializing a variable, try always to give it a value. If you don’t, the variable will get the value of the (unprepared) memory address. That’s why you have weird random numbers.

So, first of all, initialize:
int a = 0;
int b = 0;

Then, the sum “int c = a+b;” MUST come after that a and b has received their values, otherwise you’re using variables that still must have their value assigned.

// correct order
cin >> a;
cin >> b;
int c = a+b;

Answer 2

When you declare a variable, the cpu assigns to that single variable a space grabbed from the free memory. For an int type, it’s generally 4 bytes. If you don’t give it a value, the compiler will assign it a “default” value (to make debug easier), other times it won’t. So what you’re reading is a totally strange value, such as 8.

If you assign a value on the declaration, you eliminate this weird behaviour.

int a = 0; prepares all the 4 bytes belonging to the variable a to be 0.

That’s it :)

Answer 3

Before your program runs there is some code wrapped around your code that sets things up. That code left behind values in the memory a and b was assigned and those values added together happened to be 8. If you changed the order you defined things by slipping a 'int d;' in between a and b, you would get a different answer.

Answer 4

all i know for now is that you cannot add the variables before they're assigned a value in this case

write c = a+b after
cin >> a
cin >> b
not before

Answer 5

Thank you! That solved the problem easily. I would still like to know where it kept getting "8" from though, since "8" was nowhere in the code. lol

Answer 6

https://code.sololearn.com/Wnq4BuoD8aGy/?ref=app