C++ Interview : Practice Questions and Answers

<< operator is used to shift bits towards left side so if we have 1111 then on shifting this by 2 i.e. 1111 << 2 will result into 1100.

^ operator is used to take xor of two bitset variables i.e. if ith bit in both varaibles are either 1 or 0 then answer is 0 otherwise answer is 1.

When only one argument is supplied to flip() function then bit corresponding to that index only is flipped.

When no argument is supplied to flip() function i.e. function is called with empty parameters then all the bits of the bitset variable is flipped.

header provides the flip() function to flip bit(s) in a bitset variable i.e. change the bits in a bitset for example 1100 on flipping becomes 0011.

As constructor of class A is defined private and we are trying to define an object of class A which cannot call this constructor as it is private therefore the program gives an error.

In this program, we have defined a global variable an outside main function for which constructor will be called. Now as a is a global variable, therefore, the call for constructor will be before the main function hence constructor called will be printed before the Main function.

In this program, we have defined a global variable an outside main function for which constructor will be called hence the output is printed.

Unlike new malloc never calls the constructor of a class hence when we are assigning memory to an object of class A using malloc constructor is not called hence nothing is printed.

As constructor is accepting default parameter therefore the declaration of a1 and a2 both are valid hence the program runs successfully.

The declaration of object a1 needs a constructor without any arguments which is not available in the class as we have overwritten the default constructor, therefore, the program gives the error.

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As we have declared a pointer variable for class A but we have not initialized the memory to that pointer and until the memory is not initialized the constructor for the pointer variable will not be called hence nothing is printed on the screen.

No constructor should be made private because objects need to call them and as by default all the members of a class are private therefore constructor defined in the above program is private which is wrong therefore the compiler gives the error.

Copy constructor is called in all the above-mentioned criteria because in all the above cases we are somehow trying to copy one object into another.

If a programmer does not define the above constructors in a class the C++ compiler by default provides these constructors to avoid error on basic operations.

An object is an instance of a class i.e. an object represents a class i.e. what class has(data members) and what it can do(member functions).

Abstract class should have at least one pure virtual function. Therefore to declare an abstract class one should declare a pure virtual function in a class.

Though C does not allows member functions in structures but C++ allows structures to have member functions. Members of structures are public by default and those of classes are private by default. Classes can have protected data members.

Friend functions can access any member of a class without caring about the type of member i.e. without caring whether it is private, protected or public.