Copy Constructor or Copy Assignment?

1#include <iostream>
2using namespace std;
3 
4class Tag {
5public:
6    Tag() { cout << "default" << endl; }
7    Tag(const Tag& other) { cout << "copy" << endl; }
8    Tag& operator=(const Tag& other) {
9        cout << "assign" << endl;
10        return *this;
11    }
12};
13 
14int main() {
15    Tag a;
16    Tag b = a;
17    Tag c(a);
18    Tag d;
19    d = a;
20    return 0;
21}