45 practice sets · Page 1 of 3
What will be the output of the following C++ code
#include
#include
using namespace std;
int main()
{
bitset<b1(95);
bitset<b2 = b1 >> cout<<b1<<endl<<b}
00001011
11111000
01111111
00001101
Correct Answer: B — 11111000
Explanation:
<< 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.
What will be the output of the following C++ code
#include
#include
using namespace std;
int main()
{
bitset<b1(95);
bitset<b2 = b1 << cout<<b}
00001101
01110001
01111111
11111000
Correct Answer: A — 00001101
Explanation:
^ 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.
What happens when only one argument is supplied to flip() function?
All bits are flipped in a bitset
Bit corresponding to argument bit is flipped
First bit is flipped
All alternate bits are flipped in a bitset
Correct Answer: B — Bit corresponding to argument bit is flipped
Explanation:
When only one argument is supplied to flip() function then bit corresponding to that index only is flipped.
What happens when no argument is supplied to flip() function?
All alternate bits are flipped in a bitset
First bit is flipped
All bits are flipped in a bitset
All bits are flipped to 1 in a bitset
Correct Answer: C — All bits are flipped in a bitset
Explanation:
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.
What is the use of the flip function in bitset?
Used to flip a bit in a bitset
Used to flip all bits to 1
Used to flip bit(s) in a bitset
Used to flip alternate bits
Correct Answer: C — Used to flip bit(s) in a bitset
Explanation:
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.
Which of the following is correct?
Destructors can be virtual
Destructor definition starts with !
There can be more than one destructor in a class
Destructor is used to initialize objects
Correct Answer: B — Destructor definition starts with !
Explanation:
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.
How destructor overloading is done?
No chance for destructor overloading
By changing the number of parameters
By changing the parameters type
By changing both the number of parameters and their type
Correct Answer: B — By changing the number of parameters
Explanation:
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.
What will be the output of the following C++ code
#include
using namespace std;
class A{
public:
int a;
A(){
cout<<"Constructor called";
}
} a;
int main(int argc, char const *argv[])
{
return}
Nothing printed
Constructor called
Error
Segmentation fault
Correct Answer: B — Constructor called
Explanation:
In this program, we have defined a global variable an outside main function for which constructor will be called hence the output is printed.
What will be the output of the following C++ code
#include
using namespace std;
class A{
public:
int a;
A(){
cout<<"Constructor called";
}
};
int main(int argc, char const *argv[])
{
A a1 = (A)malloc(sizeof(A));
return}
Constructor called
Error
Nothing printed
Segmentation fault
Correct Answer: C — Nothing printed
Explanation:
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.
What will be the output of the following C++ code
#include
using namespace std;
class A{
public:
int a;
A(int a=0){
this->a = a;
}
};
int main(int argc, char const *argv[])
{
A aa2(10);
cout<<a2.a;
return}
010
001
100
Error
Correct Answer: A — 010
Explanation:
As constructor is accepting default parameter therefore the declaration of a1 and a2 both are valid hence the program runs successfully.
What will be the output of the following C++ code
#include
using namespace std;
class A{
public:
int a;
A(int a){
this->a = a;
}
};
int main(int argc, char const *argv[])
{
A aa2(10);
cout<<a2.a;
return}
No output
Compile time error
Run-time error
10
Correct Answer: B — Compile time error
Explanation:
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.
What will be the output of the following C++ code
#include
using namespace std;
class A{
public:
int a;
};
int main(int argc, char const *argv[])
{
A a1 = {10};
A a2 = a cout<<a1.a<<a2.a;
return}
Segmentation fault
87368746
Error
1010
Correct Answer: D — 1010
Explanation:
1010
What will be the output of the following C++ code
#include
using namespace std;
class A{
public:
A(){
cout<<"Constructor called";
}
};
int main(int argc, char const *argv[])
{
A *a;
return}
Nothing printed
Error
Constructor called
Segmentation fault
Correct Answer: A — Nothing printed
Explanation:
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.
What will be the output of the following C++ code
#include
using namespace std;
class A{
A(){
cout<<"Constructor called";
}
};
int main(int argc, char const *argv[])
{
A a;
return}
Constructor called
Segmentation fault
Error
Nothing printed
Correct Answer: C — Error
Explanation:
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.
When a copy constructor is called?
All of the mentioned
When an object of the class is passed by value to a function
When an object of the class is returned by value
When an object is constructed based on another object of the same class
Correct Answer: A — All of the mentioned
Explanation:
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.
Which of the following constructors are provided by the C++ compiler if not defined in a class?
Assignment constructor
Copy constructor
All of the mentioned
Default constructor
Correct Answer: C — All of the mentioned
Explanation:
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.
Which of the following is correct?
An object is an instance of its class
An object is an instance of the data type of the class
A class is an instance of its objects
A class is an instance of the data type that the class have
Correct Answer: A — An object is an instance of its class
Explanation:
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).
Which of the following is used to make an abstract class?
By declaring a pure virtual function in a class
By using an abstract keyword in front of a class declaration
By using virtual keyword in front of a class declaration
By declaring a virtual function in a class
Correct Answer: A — By declaring a pure virtual function in a class
Explanation:
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.
Which of the following is correct in C++?
Classes cannot have protected data members
Structure members are private by default
Class members are public by default
Structures can have member functions
Correct Answer: D — Structures can have member functions
Explanation:
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.
Which of the following is correct?
Friend functions can access private members of a class
Friend functions can access protected members of a class
Friend functions can access public members of a class
All of the mentioned
Correct Answer: D — All of the mentioned
Explanation:
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.
