c++ freshers interview questions and answers
[quote]What is C++?[/quote]
C++ released in 1985 and it is an object-oriented programming language created by Bjarne Stroustrup. C++ maintains almost all aspects of the C language while simplifying memory management and adding several features – including a new data type known as a class to allow object-oriented programming. C++ maintains the features of C which allowed for low-level memory access but also gives the programmer new tools to simplify memory management.
[quote]How do you find out if a linked-list has an end? (i.e. the list is not a cycle)[/quote]
You can find out by using 2 pointers. One of them goes 2 nodes each time. The second one goes at 1 node each time. If there is a cycle, the one that goes 2 nodes each time will eventually meet the one that goes slower. If that is the case, then you will know the linked-list is a cycle.
[quote]What is the difference between realloc() and free()?[/quote]
The free() subroutine frees a block of memory previously allocated by the malloc subroutine. Undefined results occur if the Pointer parameter is not a valid pointer. If the Pointer parameter is a null value, no action will occur. The realloc() subroutine changes the size of the block of memory pointed to by the Pointer parameter to the number of bytes specified by the Size parameter and returns a new pointer to the block. The pointer specified by the Pointer parameter must have been created with the malloc, calloc(), or realloc() subroutines and not been deallocated with the free or realloc() subroutines. Undefined results occur if the Pointer parameter is not a valid pointer.
[quote]What is function overloading and operator overloading?[/quote]
C++ enables several functions of the same name to be defined, as long as these functions have different sets of parameters (at least as far as their types are concerned). This capability is called function overloading. When an overloaded function is called, the C++ compiler selects the proper function by examining the number, types, and order of the arguments in the call. Function overloading is commonly used to create several functions of the same name that perform similar tasks but on different data types.
Operator overloading allows existing C++ operators to be redefined so that they work on objects of user-defined classes. Overloaded operators are syntactic sugar for equivalent function calls.
[quote]What is the difference between function declaration and definition?[/quote]
The declaration tells the compiler that at some later point we plan to present the definition of this declaration.
E.g.: void stars () //function declaration
The definition contains the actual implementation.
void stars(); // function declarator
int main()
{
stars();
return 0;
}
void stars()
{
//function body
for(int j=10; j > =0; j--)
cout << *;
cout << endl;
}
[quote]What are the advantages of inheritance?[/quote]
It permits code reusability. Reusability saves time in program development. It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional.
[quote]How do you write a function that can reverse a linked-list?[/quote]
void reverselist(void)
{
if(head==0)
return;
if(head->next==0)
return;
if(head->next==tail)
{
head->next = 0;
tail->next = head;
}
else
{
node* pre = head;
node* cur = head->next;
node* curnext = cur->next;
head->next = 0;
cur-> next = head;
for(; curnext!=0; )
{
cur->next = pre;
pre = cur;
cur = curnext;
curnext = curnext->next; }
curnext->next = cur;
}
}
[quote]What do you mean by inline function?[/quote]
The idea behind inline functions is to insert the code of a called function at the point where the function is called. If done carefully, this can improve the application’s performance in exchange for increased compile time and possibly an increase in the size of the generated binary executables.
[quote]Write a program that asks for user input from 5 to 9 then calculates the average[/quote]
#include "iostream.h"
int main()
{
int MAX = 4;
int total = 0;
float average;
int numb;
for (int i=0; i<MAX; i++)
{
cout << "Please enter your input between 5 and 9: "; cin >> numb;
while ( numb<5 || numb>9)
{
cout << "Invalid input, please re-enter: ";
cin >> numb;
}
total = total + numb;
}
average = (float)total/MAX;
cout << "The average number is: " << average << "\n";
return 0;
}
[quote]Write a shortcode using C++ to print out all odd number from 1 to 100 using a for loop[/quote]
#include <iostream.h>
int main()
{
for( unsigned int i = 1; i < = 100; i++ )
if( i & 0x00000001 )
cout << i << \",\";
return 0;
}
[quote]What is public, protected, private?[/quote]
public, protected and private are three access specifier in C++. public data members and member functions are accessible outside the class. Protected data members and member functions are only available to derived classes. private data members and member functions can’t be accessed outside the class. However there is an exception can be using friend classes.
[quote]Write a function that swaps the values of two integers, using int* as the argument type.[/quote]
void swap(int* a, int*b)
{
int t;
t = *a;
*a = *b;
*b = t;
}
[quote]How to check whether a linked list is circular?[/quote]
Create two pointers, each set to the start of the list. Update each as follows:
while (pointer1)
{
pointer1 = pointer1->next;
pointer2 = pointer2->next;
if (pointer2)
pointer2=pointer2->next;
if (pointer1 == pointer2)
{
print ("circular\n\n");
break;
}
}
If a list is circular, at some point pointer2 will wrap around and be either at the item just before pointer1, or the item before that. Either way, it’s either 1 or 2 jumps until they meet.
c++ interview questions and answers for freshers
[quote]What is virtual constructors/destructors?[/quote]
If an object (with a non-virtual destructor) is destroyed explicitly by applying the delete operator to a base-class pointer to the object, the base class destructor function (matching the pointer type) is called on the object.
There is a simple solution to this problem – declare a virtual base-class destructor. This makes all derived-class destructors virtual even though they don’t have the same name as the base-class destructor. Now, if the object in the hierarchy is destroyed explicitly by applying the delete operator to a base-class pointer to a derived-class object, the destructor for the appropriate class is called.
Constructors cannot be virtual. Declaring a constructor as a virtual function is a syntax error.
[quote]Does c++ support multilevel and multiple inheritances?[/quote]
Yes.
[quote]What are the advantages of inheritance?[/quote]
- It permits code reusability.
- Reusability saves time in program development.
- It encourages the reuse of proven and debugged high-quality software, thus reducing problem after a system becomes functional.
[quote]What is the difference between an Array and a List?[/quote]
- An array is a collection of homogeneous elements. The list is a collection of heterogeneous elements.
- For Array memory allocated is static and continuous.
- For List memory allocated is dynamic and Random.
[quote]Does c++ support multilevel and multiple inheritances?[/quote]
Yes.
[quote]What is a template?[/quote]
Templates allow creating generic functions that admit any data type as parameters and return value without having to overload the function with all the possible data types. Until a certain point, they fulfill the functionality of a macro.
[quote]What is a constructor and how it might be called?[/quote]
A constructor is a member function of the class, with the name of the function being the same as the class name. It also specifies how the object should be initialized.
Ways of calling constructor:
- Implicitly: automatically by the compiler when an object is created
- Calling the constructors explicitly is possible, but it makes the code unverifiable.
[quote]What is the difference between new, delete and alloc(), free()?[/quote]
- new and delete are operators in c++ while malloc() and free() are functions.
- No need to allocate the memory while using new but in malloc() we have to use sizeof().
- new will initialize the new memory to 0 but malloc() gives random value in the newly allocated memory location
[quote]What is the difference between class and structure?[/quote]
Initially, in C a structure was used to bundle different type of data types together to perform a particular functionality. But C++ extended the structure to contain functions also. The major difference is that all declarations inside a structure are by default public but in a class by default all the members inside the class are private.
[quote]What is RTTI?[/quote]
Runtime type identification (RTTI) lets you find the dynamic type of an object when you have only a pointer or a reference to the base type. RTTI is the official way in standard C++ to discover the type of an object and to convert the type of a pointer or reference (that is, dynamic typing).
[quote]What is encapsulation?[/quote]
Packaging an object’s variables within its methods is called encapsulation.
[quote]What is an object?[/quote]
An object is a software bundle of variables and related methods. Objects have state and behavior.
[quote]How can you tell what shell you are running on a UNIX system?[/quote]
You can do the Echo $RANDOM. It will return an undefined variable if you are from the C-Shell, just a return prompt if you are from the Bourne shell, and a 5 digit random numbers if you are from the Korn shell. You could also do a ps -l and look for the shell with the highest PID.
[quote]What is namespace?[/quote]
Namespaces allow us to group a set of global classes, objects, and functions under a name. To say it somehow, they serve to split the global scope in sub-scopes known as namespaces. The form to use namespaces is:
namespace identifier { namespace-body }
Where identifier is any valid identifier and namespace-body is the set of classes, objects, and functions that are included within the namespace.
[quote]What is a Copy Constructor and when is it called?[/quote]
A copy constructor is a method that accepts an object of the same class and copies it’s data members to the object on the left part of assignment:
class Point2D
{
int x;
int y;
public int color;
protected bool pinned;
public Point2D() : x(0) , y(0) {} //default (no argument) constructor
public Point2D( const Point2D & ) ;
};
Point2D::Point2D( const Point2D & p )
{
this->x = p.x;
this->y = p.y;
this->color = p.color;
this->pinned = p.pinned;
}
int main()
{
Point2D MyPoint;
MyPoint.color = 345;
Point2D AnotherPoint = Point2D( MyPoint ); // now AnotherPoint has color = 345
return 0;
}
[quote]What is a virtual class and friend class?[/quote]
Friend classes are used when two or more classes are designed to work together and need access to each other’s implementation in ways that the rest of the world shouldn’t be allowed to have. In other words, they help keep private things private.
freshers c++ interview questions and answers
[quote]What is the word you will use when defining a function in the base class to allow this function to be a polymorphic function?[/quote]
virtual
[quote]What do you mean by binding of data and functions?[/quote]
Encapsulation.
[quote]What is the difference between an object and a class?[/quote]
Classes and objects are separate but related concepts. Every object belongs to a class and every class contains one or more related objects.
- A Class is static. All of the attributes of a class are fixed before, during, and after the execution of a program. The attributes of a class don’t change.
- The class to which an object belongs is also (usually) static. If a particular object belongs to a certain class at the time that it is created then it almost certainly will still belong to that class right up until the time that it is destroyed.
- An Object, on the other hand, has a limited lifespan. Objects are created and eventually destroyed. Also during that lifetime, the attributes of the object may undergo significant change.
[quote]What is a class?[/quote]
Class is a user-defined data type in C++. It can be created to solve a particular kind of problem. After creation, the user need not know the specifics of the working of a class.
[quote]What is friend function?[/quote]
As the name suggests, the function acts as a friend to a class. As a friend of a class, it can access its private and protected members. A friend function is not a member of the class. But it must be listed in the class definition.
[quote]What is abstraction?[/quote]
Abstraction is of the process of hiding unwanted details from the user.
[quote]What are virtual functions?[/quote]
A virtual function allows derived classes to replace the implementation provided by the base class. The compiler makes sure the replacement is always called whenever the object in question is actually of the derived class, even if the object is accessed by a base pointer rather than a derived pointer. This allows algorithms in the base class to be replaced in the derived class, even if users don’t know about the derived class.
[quote]What is the difference between an external iterator and an internal iterator? Describe the advantage of an external iterator.[/quote]
An internal iterator is implemented with member functions of the class that has items to step through. An external iterator is implemented as a separate class that can be “attach” to the object that has items to step through. An external iterator has the advantage that many difference iterators can be active simultaneously on the same object.
[quote]What is a scope resolution operator?[/quote]
A scope resolution operator (::), can be used to define the member functions of a class outside the class.
[quote]What is the difference between char a[] = “string” and char *p = “string”?[/quote]
In the first case, 6 bytes are allocated to the variable a which is fixed, whereas in the second case if *p is assigned to some other value the allocate memory can change.
[quote]How do you link a C++ program to C functions?[/quote]
By using the extern “C” linkage specification around the C function declarations.
[quote]How does throwing and catching exceptions differ from using setjmp and longjmp?[/quote]
The throw operation calls the destructors for automatic objects instantiated since entry to the try block.
[quote]What is a mutable member?[/quote]
One that can be modified by the class even when the object of the class or the member function doing the modification is const.
[quote]What is an explicit constructor?[/quote]
A conversion constructor declared with the explicit keyword. The compiler does not use an explicit constructor to implement an implied conversion of types. It’s purpose is reserved explicitly for construction.
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