Creating objects in C++ - Practice Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of object creation and member access

What is the output of this C++ code when creating an object and accessing its member?

C++

class Box {
public:
    int length;
    Box(int l) : length(l) {}
};

int main() {
    Box b(10);
    std::cout << b.length << std::endl;
    return 0;
}

A 0

B Runtime error

C Compilation error

D 10

💡 Hint

Look at how the constructor initializes the length member.

The constructor sets length to 10, so printing b.length outputs 10.

❓ Predict Output

intermediate

Output when creating an object with default constructor

What will be the output of this code snippet?

C++

class Point {
public:
    int x, y;
    Point() { x = 5; y = 7; }
};

int main() {
    Point p;
    std::cout << p.x << "," << p.y << std::endl;
    return 0;
}

A Compilation error

B 0,0

C 5,7

D Garbage values

💡 Hint

The default constructor sets x and y explicitly.

The default constructor assigns 5 to x and 7 to y, so output is '5,7'.

❓ Predict Output

advanced

Output of object creation with private constructor

What happens when you try to compile and run this code?

C++

class Secret {
private:
    Secret() {}
public:
    static Secret create() { return Secret(); }
};

int main() {
    Secret s = Secret::create();
    return 0;
}

A Compiles and runs without output

B Compilation error: constructor is private

C Runtime error

D Linker error

💡 Hint

The static method can access the private constructor.

The private constructor is accessible inside the static create method, so object creation works fine.

❓ Predict Output

advanced

Output of object creation with deleted copy constructor

What will happen when this code is compiled and run?

C++

class NoCopy {
public:
    NoCopy() {}
    NoCopy(const NoCopy&) = delete;
};

int main() {
    NoCopy a;
    NoCopy b = a;
    return 0;
}

A Runs and copies object

B Compilation error due to deleted copy constructor

C Runtime error

D Linker error

💡 Hint

Copying is disabled explicitly.

The copy constructor is deleted, so copying object 'a' to 'b' causes a compilation error.

🧠 Conceptual

expert

Number of objects created in this code

How many objects are created in total when this code runs?

C++

class Sample {
public:
    Sample() {}
};

Sample createSample() {
    Sample s;
    return s;
}

int main() {
    Sample a = createSample();
    return 0;
}

A 2

B 1

C 3

D 0

💡 Hint

Consider the local object and the returned object.

One object is created inside createSample, and another is created when returning it to 'a'.