Concept of Value and Reference

 there are two ways to represent a variable: by value and by reference.

When a variable is passed by value, a copy of the variable is created and passed to the function. Any changes made to the copy do not affect the original variable. Here's an example:

int main() {
    int a = 5;
    int b = 10;
    swapByValue(a, b);
std::cout << "a: " 
<< a << " b: "<< b<<std::endl;
    return 0;
}

void swapByValue(int x, int y){
    int temp = x;
    x = y;
    y = temp;
}

Here, the variables a and b are passed by value to the swapByValue function. The function swaps the values of the passed variables, but the values of a and b in the main function remain unchanged. The output will be "a: 5 b: 10".

On the other hand, when a variable is passed by reference, a reference to the original variable is passed to the function. Any changes made to the variable inside the function will affect the original variable. Here's an example:

int main() {
    int a = 5;
    int b = 10;
    swapByReference(a, b);
std::cout << "a: " 
<< a << "b: "<< b<<std::endl;
    return 0;
}

void swapByReference(int &x, int &y){
    int temp = x;
    x = y;
    y = temp;
}

Here, the variables a and b are passed by reference to the swapByReference function. The function swaps the values of the passed variables, and the values of a and b in the main function are also changed. The output will be "a: 10 b: 5".

It's worth noting that in C++, when an object is passed by value, a copy of the object is created, but when an object is passed by reference, a reference to the original object is passed.