Fixing this simple code - c++

Question

I'm a beginner at coding and I can't fix this code and I'm going crazy. It keeps telling me certain variables were not declared and i'm not sure how to fix it.
#include <iostream>
using namespace std;
int main()
{
int (a = 0), sum;{
cout << "This program should read all integer numbers ";
cout << "to sum until a negative number is entered\n";
exit(0);
}
while(a < 0) {
cout << "Enter an integer number: ";
cin >> a;
sum += a;
}
cout << "The sum is sum\n";
return 0;
}

Answer 1

You did not initialize sum, so it could start with any value.
You have extra layers of pointless { } around for no reason.
Your final cout statement does not actually print the varaible.
Change it to: cout << "The sum is " << sum << "\n";
#include <iostream>
using namespace std;
int main()
{
int a = 0, sum = 0;
cout << "This program should read all integer numbers ";
cout << "to sum until a negative number is entered\n";
do {
cout << "Enter an integer number: ";
cin >> a;
if (a > 0)
{
sum += a;
cout << "The sum is currently: " << sum << "; but this is not yet the final value.\n";
}
} while(a > 0) ;
cout << "The sum is " << sum << "\n";
return 0;
}

Answer 2

Lots of gotchas with your code.
Issues I found and corrected:
You have extra parentheses and curly brackets.
You didn't initialize the variable called sum
You initialize the variable called a to 0 but your loop will only execute while a is less than 0
I had to #include "stdafx.h" above where you included iostream
The line that says "The sum is sum" - the second sum should be outside the double quotes so that it will be treated as a variable rather than text.
This code works, please compare it to yours:
#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
int a = 0, sum = 0;
cout << "This program should read all integer numbers ";
cout << "to sum until a negative number is entered\n";
while (a <= 0) {
cout << "Enter an integer number: ";
cin >> a;
sum += a;
}
cout << "The sum is " << sum << "\n";
return 0;
}