C++ MCQs

Question 1

What is the purpose of a constructor in C++?

Accepted Answer

To initialize an object's data members automatically when the object is created

Answer

To destroy an object when it goes out of scope

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To define static class members only

Answer

To convert an object into a different data type

Question 2

What is the difference between a pointer and a reference in C++?

Accepted Answer

A pointer can be reassigned to point to a different variable and can be null, while a reference must be initialized when declared and cannot be changed to refer to another variable

Answer

A reference can be reassigned freely, while a pointer cannot

Answer

Both behave identically in every situation

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A pointer can only be used with primitive data types

Question 3

What is a virtual function in C++?

Accepted Answer

A member function that can be overridden in a derived class and is resolved at runtime based on the actual object type

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A function that can never be overridden by a derived class

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A function that exists only in abstract classes

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A function that runs automatically before the main function

Question 4

What is the purpose of a destructor in C++?

Accepted Answer

To automatically release resources and clean up when an object goes out of scope or is deleted

Answer

To initialize an object when it is first created

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To copy one object's data into another object

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To compare two objects for equality

Question 5

What is function overloading in C++?

Accepted Answer

Defining multiple functions with the same name but different parameter types or counts within the same scope

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Defining a single function that can never be called more than once

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Rewriting a base class function in a derived class with the same signature

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Declaring a function without specifying its return type

Question 6

What is the purpose of the 'const' keyword when applied to a function parameter in C++?

Accepted Answer

It prevents the function from modifying the value of that parameter

Answer

It forces the parameter to be passed by reference

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It makes the parameter a static variable

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It automatically initializes the parameter to zero

Question 7

What is the diamond problem in C++?

Accepted Answer

An ambiguity that arises when a class inherits from two classes that both inherit from a common base class

Answer

A compiler error that occurs when a class has too many constructors

Answer

A memory leak caused by improper use of pointers

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An issue that occurs only with template classes

Question 8

What is the purpose of the 'new' operator in C++?

Accepted Answer

To dynamically allocate memory on the heap for an object or array at runtime

Answer

To create a new class definition

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To declare a new local variable on the stack

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To permanently delete an object from memory

Question 9

What is operator overloading in C++?

Accepted Answer

The ability to redefine how standard operators, such as +, behave when used with user-defined types

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The ability to change the precedence of built-in operators

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A technique for combining two unrelated classes into one

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A restriction that prevents operators from being used with custom classes

Question 10

What is the purpose of the 'this' pointer in C++?

Accepted Answer

It points to the current object on which a member function is being called

Answer

It points to the base class of the current object

Answer

It stores the memory address of the main function

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It refers to a static member shared across all objects

Question 11

What is a template in C++ used for?

Accepted Answer

To write generic, reusable functions or classes that work with any data type without rewriting code for each type

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To define a fixed layout for a graphical user interface

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To create a backup copy of a class definition

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To restrict a function to only accept integer arguments

Question 12

What is the difference between a struct and a class in C++?

Accepted Answer

Members of a struct are public by default, while members of a class are private by default

Answer

Members of a class are public by default, while members of a struct are private by default

Answer

A struct cannot have member functions, while a class can

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Both are functionally identical in every respect including default access

Question 13

What does the C++ Standard Template Library (STL) provide?

Accepted Answer

A collection of pre-built generic classes and functions, such as containers, iterators, and algorithms

Answer

A set of tools for compiling C++ code into machine language

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A graphical interface for writing C++ programs

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A library exclusively for handling file input and output

Question 14

What is the purpose of the 'friend' keyword in C++?

Accepted Answer

It grants a function or class access to the private and protected members of another class

Answer

It marks a function as unable to be called from outside its class

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It creates a copy of an existing class

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It prevents a class from being inherited

Question 15

What happens if a class in C++ does not explicitly define a destructor?

Accepted Answer

The compiler automatically generates a default destructor that performs basic cleanup

Answer

The program will fail to compile

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All memory allocated by the object is automatically leaked

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The class cannot be instantiated at all

Question 16

What is the difference between pass by value and pass by reference in C++ function calls?

Accepted Answer

Pass by value creates a copy of the argument, while pass by reference allows the function to modify the original variable directly

Answer

Pass by reference always creates a copy, while pass by value modifies the original

Answer

Both approaches behave identically in terms of memory usage

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Pass by value can only be used with pointers

Question 17

What is the purpose of namespaces in C++?

Accepted Answer

To group related identifiers together and avoid naming conflicts between different parts of a program

Answer

To define the memory layout of a class

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To specify the access level of class members

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To automatically optimize code for faster execution

Question 18

What is a smart pointer in modern C++?

Accepted Answer

An object that automatically manages the memory of a dynamically allocated resource, releasing it when no longer needed

Answer

A pointer that can only point to integer variables

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A pointer that automatically increases its own value

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A pointer used exclusively for function arguments

Question 19

What is the difference between compile-time polymorphism and runtime polymorphism in C++?

Accepted Answer

Compile-time polymorphism, such as function overloading, is resolved during compilation, while runtime polymorphism, such as virtual functions, is resolved during program execution

Answer

Runtime polymorphism is always resolved during compilation instead

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Compile-time polymorphism only applies to constructors

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Both types of polymorphism are resolved at the exact same stage

Question 20

What is the purpose of an inline function in C++?

Accepted Answer

To suggest to the compiler that the function's code be inserted directly at the call site to potentially reduce function call overhead

Answer

To force a function to run only once during the entire program

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To prevent a function from being called recursively

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To automatically make a function thread safe

C++ MCQ Questions