C + + Rectification Textbook Teaching Practice example 1.2 two number and why Sum=a+b;sum value is 65538

Chapter I.

#include <iostream>
using namespace Std;

int main () {
int a,b,sum;
Sum=a+b;
cin>>a>>b;
cout<< "a+b=" <<sum<<endl;
return 0;
}

Reason Sum=a+b; This statement is not in position, and the variable A, B, is added when there is no assignment, beyond the int maximum range. Can only get the maximum value 65538

#include <iostream>
using namespace Std;

int main () {
int a,b,sum;
cin>>a>>b;

Sum=a+b;

cout<< "a+b=" <<sum<<endl;
return 0;
}

C + + Rectification Textbook Teaching Practice example 1.2 two number and why Sum=a+b;sum value is 65538