1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
#include<iostream>
using namespace std;

class Test
{
    public:
    Test() {}
    Test(const Test &t)
    {
        cout<<"Copy constructor called "<<endl;
    }
    Test& operator = (const Test &t)
    {
        cout<<"Assignment operator called "<<endl;
    }
};

int main()
{
    Test t1, t2;
    t2 = t1;  // calls assignment operator, same as "t2.operator=(t1);"
    Test t3 = t1;  // calls copy constructor, same as "Test t3(t1);"
    return 0;
}

output:

1
2
Assignment operator called
Copy constructor called

Copy constructor is called when a new object is created from an existing object, as a copy of the existing object (see this G-Fact). And assignment operator is called when an already initialized object is assigned a new value from another existing object.