Output of C++ Program | Set 4

Difficulty Level: Rookie

Predict the output of below C++ programs.

Question 1

#include<iostream> using namespace std;   int x = 10; void fun() {     int x = 2;     {         int x = 1;         cout << ::x << endl;     } }   int main() {     fun();     return 0; }

Output: 10
If Scope Resolution Operator is placed before a variable name then the global variable is referenced. So if we remove the following line from the above program then it will fail in compilation.

  int x = 10;

Question 2

#include<iostream> using namespace std; class Point { private:     int x;     int y; public:     Point(int i, int j);  // Constructor };   Point::Point(int i = 0, int j = 0)  {     x = i;     y = j;     cout << "Constructor called"; }   int main() {    Point t1, *t2;    return 0; }

Output: Constructor called.
If we take a closer look at the statement “Point t1, *t2;:” then we can see that only one object is constructed here. t2 is just a pointer variable, not an object.

Question 3

#include<iostream> using namespace std;   class Point { private:     int x;     int y; public:     Point(int i = 0, int j = 0);    // Normal Constructor     Point(const Point &t); // Copy Constructor };   Point::Point(int i, int j)  {     x = i;     y = j;     cout << "Normal Constructor called\n"; }   Point::Point(const Point &t) {    y = t.y;    cout << "Copy Constructor called\n"; }   int main() {    Point *t1, *t2;    t1 = new Point(10, 15);    t2 = new Point(*t1);    Point t3 = *t1;    Point t4;    t4 = t3;    return 0; }

Output:
Normal Constructor called
Copy Constructor called
Copy Constructor called
Normal Constructor called

See following comments for explanation:

Point *t1, *t2;   // No constructor call t1 = new Point(10, 15);  // Normal constructor call t2 = new Point(*t1);   // Copy constructor call Point t3 = *t1;  // Copy Constructor call Point t4;   // Normal Constructor call t4 = t3;   // Assignment operator call

Please write comments if you find any of the answers/explanations incorrect, or you want to share more information about the topics discussed above