pass by reference vs pass by value

pointer_example.cpp

#include <iostream>

using namespace std;

struct record_t
{
    int id;
};

void Mutable(record_t &record);
void Immutable(record_t record);

int main()
{
    record_t record;
    record.id = 0;
    record_t *ptr = &record;

    cout << "Record" << endl;
    cout << "Before Mutable: " << &record << ' ' << record.id << endl;
    Mutable(record);
    cout << "After Mutable:  " << &record << ' ' << record.id << endl;
    cout << endl;
    cout << "Before Immutable: " << &record << ' ' << record.id << endl;
    Immutable(record);
    cout << "After Immutable:  " << &record << ' ' << record.id << endl;
    cout << endl;

    ptr->id = 0;

    cout << "Pointer" << endl;
    cout << "Before Mutable: "
         << ptr << ' ' << ptr->id << ' '
         << &record << ' ' << record.id << endl;
    Mutable(*ptr);
    cout << "After Mutable:  " << ptr << ' ' << ptr->id << ' '
         << &record << ' ' << record.id << endl;

    cout << endl;

    cout << "Before Immutable: " << ptr << ' ' << ptr->id << ' '
         << &record << ' ' << record.id << endl;
    Immutable(*ptr);
    cout << "After Immutable:  " << ptr << ' ' << ptr->id << ' '
         << &record << ' ' << record.id << endl;
    cout << endl;

    cout << "Address of record:  " << ptr << endl;
    cout << "Address of pointer: " << &ptr << endl;


    return 0;
}

void Mutable(record_t &record)
{
    record.id = 1;

    cout << "Inside Mutable: " << &record << ' ' << record.id << endl;
}

void Immutable(record_t record)
{
    record.id = 2;

    cout << "Inside Immutable: " << &record << ' ' << record.id << endl;
}