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What is C++
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C++ is created by Bjarne Stroustrup of AT&T Bell Labs
as an extension of C, C++ is an object-oriented computer language used in the
development of enterprise and commercial applications. Microsoft’s Visual C++
became the premier language of choice among developers and programmers.
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2.
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What are the basic concepts of object oriented
programming?
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It is necessary to understand
some of the concepts used extensively in object oriented programming.These
include
- Objects
- Classes
- Data abstraction and
encapsulation
- Inheritance
- Polymorphism
- Dynamic Binding
- Message passing
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3.
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Define inheritance?
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The mechanism of deriving a new class (derived) from an
old class (base class) is called inheritance. It allows the extension and
reuse of existing code without having to rewrite the code from scratch.
Inheritance is the process by which objects of one class acquire properties
of objects of another class.
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4.
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Define polymorphism?
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Polymorphism means one name, multiple forms. It allows us
to have more than one function with the same name in a program.It allows us
to have overloading of operators so that an operation can exhibit different
behaviours in different instances.
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5.
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What is encapsulation?
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The wrapping up of data and functions into a single unit
(called class) is known as encapsulation. Encapsulation containing and hiding
information about an object, such as internal data structures and code.
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6.
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What is message passing?
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An object oriented program consists of a set of objects
that communicate with each other. Message passing involves specifying the
name of the object, the name of the function and the information to be sent.
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7.
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What are tokens in C++?
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The smallest individual units of
a program is known as tokens. c++ has the following tokens :
- Keywords
- Identifiers
- Constants
- Strings
- Operators
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8.
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What is the use of enumerated data type?
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An enumerated data type is another user defined type which
provides a way for attaching names to numbers thereby increasing
comprehensibility of the code. The enum keyword automatically enumerates a
list of words by assigning them values 0,1,2, and so on.
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9.
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What is the use of default constructor?
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A constructors that accepts no parameters is called the
default constructor.If no user-defined constructor exists for a class A and
one is needed, the compiler implicitly declares a default parameterless
constructor A::A(). This constructor is an inline public member of its class.
The compiler will implicitly define A::A() when the compiler uses this constructor
to create an object of type A. The constructor will have no constructor
initializer and a null body.
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10.
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Define Constructors?
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A constructor is a member function with the same name as
its class. The constructor is invoked whenever an object of its associated
class is created.It is called constructor because it constructs the values of
data members of the class.
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ow variable declaration in c++ differs that in c?
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C requires all the variables to be declared at the
beginning of a scope but in c++ we can declare variables anywhere in the
scope. This makes the programmer easier to understand because the variables
are declared in the context of their use.
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12.
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Define destuctors?
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A destructor is called for a class object when that object
passes out of scope or is explicitly deleted.A destructors as the name
implies is used to destroy the objects that have been created by a
constructors.Like a constructor , the destructor is a member function whose
name is the same as the class name but is precided by a tilde.
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13.
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What is a class?
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A class is a collection of objects.
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14.
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what is the difference between c &c++?
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c++ ia an object oriented programing but c is a procedure
oriented programing.c is super set of c++. c can't suport inheritance,function
overloading, method overloading etc. but c++ can do this.In c-programe the
main function could not return a value but in the c++ the main function shuld
return a value.
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15.
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What is copy constructor?
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Copy constructor is a constructor function with the same
name as the class and used to make deep copy of objects.
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16.
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What is default constructor?
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A default constructor is a constructor that either has no
parameters, or if it has parameters, all the parameters have default values.
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17.
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What is a scope resolution operator?
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The scope resolution operator permits a program to
reference an identifier in the global scope that has been hidden by another
identifier with the same name in the local scope.
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18.
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What is the difference between Object and Instance?
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An instance of a user-defined type is called an object. We
can instantiate many objects from one class.
An object is an instance of a class.
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19.
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What is the difference between macro and iniine?
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Inline follows strict parameter type checking, macros do
not.
Macros are always expanded by preprocessor, whereas compiler may or may not
replace the inline definitions.
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20.
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How variable declaration in c++ differs that in c?
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C requires all the variables to be declared at the
beginning of a scope but in c++ we can declare variables anywhere in the
scope. This makes the programmer easier to understand because the variables
are declared in the context of their use.
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21.
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What is multiple inheritance?
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A class can inherit properties from more than one class
which is known as multiple inheritance.
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22.
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what is the use of virtual destructor in c++?
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A destructor is automatically called when the object is
destroyed. A virtual destructor in C++ is used primarily to prevent resource
leaks by performing a clean-up of the object.
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23.
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What do you mean by reference variable in c++?
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A reference variable provides an alias to a previously
defined variable.
Data -type & reference-name = variable name
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24.
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What do you mean by implicit conversion?
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- Whenever data types
are mixed in an expression then c++ performs the conversion
automatically.
- Here smaller type is
converted to wider type.
- Example : in case of
integer and float integer is converted into float type.
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25.
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What are virtual functions?
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- The virtual fuctions
must be members of some class.
- They cannot be static
members.
- They are accessed by
using object pointers.
- A virtual function can
be a friend of another class.
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26.
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What is the difference between class and structure?
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- By default, the members
ot structures are public while that tor class is private.
- structures doesn’t
provide something like data hiding which is provided by the classes.
- structures contains
only data while class bind both data and member functions.
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27.
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What are storage qualifiers in C++ ?
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ConstKeyword indicates that memory once
initialized, should not be altered by a program.
Volatile keyword indicates that the value in the memory location can
be altered even though nothing in the program.
Mutable keyword indicates that particular member of a structure or
class can be altered even if a particular structure variable, class, or class
member function is constant.
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28.
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What is virtual class and friend class?
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Friend classes are used when two or more classes and
virtual base class aids in multiple inheritance.
Virtual class is used for run time polymorphism when object is linked to
procedure call at run time.
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29.
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what is an abstract base class?
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An abstract class is a class that is designed to be
specifically used as a base class. An abstract class contains at least one
pure virtual function.
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30.
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What is dynamic binding?
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Dynamic binding (also known as late binding) means that
the code associated with a given procedure call is not known until the time
of the call at run time.It is associated with polymorphism and inheritance.
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1.
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what is difference between function overloading and
operator overloading?
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A function is overloaded when same name is given to
different function.
While overloading a function, the return type of the functions need to be the
same.
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32.
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What are the advantages of inheritance?
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- Code reusability
- Saves time in program
development.
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33.
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What is a dynamic constructor?
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The constructor can also be used to allocate memory while
creating objects. Allocation of memory to objects at the time of their
construction is known as dynamic construction of objects.The memory is
allocated with the help of the new operator.
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34.
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What is the difference between an Array and a List?
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The main difference between an array and a list is how
they internally store the data. whereas Array is collection of homogeneous
elements. List is collection of heterogeneous elements.
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35.
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What is the use of ‘using’ declaration?
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A using declaration makes it possible to use a name from a
namespace.
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36.
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What is the difference between a template class and class
template?
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Template classA generic definition or a
parameterized class not instantiated until the client provides the needed
information. It’s jargon for plain templates.
Class templateA class template specifies how individual classes can
be constructed much like the way a class specifies how individual objects can
be constructed. It’s jargon for plain classes.
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37.
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What is friend function?
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The function declaration should be preceded by the keyword
friend.The function definitions does not use either the keyword or the scope
operator ::. The functions that are declared with the keyword friend as
friend function.Thus, a friend function is an ordinary function or a member
of another class.
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38.
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What is a scope resolution operator?
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A scope resolution operator (::), can be used to define
the member functions of a class outside the class.
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39.
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What do you mean by pure virtual functions?
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A pure virtual member function is a member function that
the base class forces derived classes to provide. Any class containing any
pure virtual function cannot be used to create object of its own type.
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40.
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What is a conversion constructor?
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A converting constructor is a single-parameter constructor
that is declared without the function specifier explicit. The compiler uses
converting constructors to convert objects from the type of the first
parameter to the type of the converting constructor’s class.
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41.
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What is a container class? What are the types of container
classes?
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A container class is a class that is used to hold objects
in memory or external storage. A container class acts as a generic holder. A
container class has a predefined behavior and a wellknown interface. A
container class is a supporting class whose purpose is to hide the topology
used for maintaining the list of objects in memory. When a container class
contains a group of mixed objects, the container is called a heterogeneous
container; when the container is holding a group of objects that are all the
same, the container is called a homogeneous container.
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42.
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What is Associative container?
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Associative containers are
designed to support direct access to elements using keys. They are not
sequential. There are four types of associatives containers :
- Set
- Multiset
- Map
- Multimap
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43.
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What is an iterator?
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Iterators are like pointers. They are used to access the
elements of containers thus providing a link between algorithms and
containers. Iterators are defined for specific containers and used as
arguments to algorithms.
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44.
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What are the defining traits of an object-oriented
language?
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The defining traits of an
object-oriented langauge are :
- Encapsulation
- Inheritance
- Polymorphism
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45.
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Name some pure object oriented languages?
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- Smalltalk
- Java
- Eiffel
- Sather
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46.
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What is this pointer?
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It is a pointer that points to the current object. This
can be used to access the members of the current object with the help of the
arrow operator.
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47.
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What is encapsulation?
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Encapsulation (or information hiding) is the process of
combining data and functions into a single unit called class.
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48.
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What is problem with Runtime type identification?
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The run time type identification comes at a cost of
performance penalty. Compiler maintains the class.
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49.
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What are the differences between new and malloc?
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- New initializes the
allocated memory by calling the constructor. Memory allocated with new
should be released with delete.
- Malloc allocates
uninitialized memory.
- The allocated memory
has to be released with free.new automatically calls the constructor
while malloc(dosen’t)
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50.
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What is conversion operator?
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You can define a member function of a class, called a
conversion function, that converts from the type of its class to another
specified type.
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51.
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What is difference between template and macro?
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A template can be used to create a family of classes or
function.A template describes a set of related classes or set of related
functions in which a list of parameters in the declaration describe how the
members of the set vary.
Identifiers that represent statements or expressions are called macros.
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52.
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What is reference?
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Reference is a name that acts as an alias, or alternative
name, for a previously defined variable or an object.
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53.
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What are the access specifier in c++?
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There are three types of access
specifier in c++ . They are
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54.
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What is difference between C++ and Java?
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- C++ has pointers
Java does not.
- Java is the platform
independent as it works on any type of operating systems.
- java has no pointers
where c ++ has pointers.
- Java has garbage
collection C++ does not.
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55.
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What is namespace?
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The C++ language provides a single global
namespace.Namespaces allow to group entities like classes, objects and
functions under a name.
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56.
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What is an explicit constructor?
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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.Explicit constructors are simply constructors that cannot take
part in an implicit conversion.
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57.
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What is the use of storage class specifiers?
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A storage class specifier is used
to refine the declaration of a variable, a function, and parameters. The
following are storage class specifiers :
- auto
- register
- static
- extern
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58.
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what is assignment operator in c++?
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Default assignment operator handles assigning one object
to another of the same class. Member to member copy (shallow copy).
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59.
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Can destructor be private?
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Yes destructors can be private. But according it is not
advisable to have destructors to be private.
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60.
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What is strstream?
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stringstream provides an interface to manipulate strings
as if they were input/output streams.
‹ strstream› to define several classes that support iostreams operations on
sequences stored in an allocated array of char object.
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61.
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What are the types of STL containers?
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- deque
- hash map
- hashmultimap
- hash_multiset
- hashset
- list
- map
- multimap
- multiset
- set
- vector
.
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62.
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What is the difference between method overloading and
method overriding?
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Overloading a method (or function) in C++ is the
ability for functions of the same name to be defined as long as these methods
have different signatures (different set of parameters).
Method overriding is the ability of the inherited class rewriting the
virtual method of the base class.
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63.
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What do you mean by inline function?
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An inline function is a function that is expanded inline
when invoked.ie. the compiler replaces the function call with the
corresponding function code. An inline function is a function that is
expanded in line when it is invoked. That is the compiler replaces the
function call with the corresponding function code (similar to macro).
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64.
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What is a template?
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A template can be used to create a family of classes or
function.A template describes a set of related classes or set of related
functions in which a list of parameters in the declaration describe how the
members of the set vary.
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65.
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What is a copy constructor and when is it called?
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A copy constructor is a method that accepts an object of
the same class and copies it members to the object on the left part of
assignement.
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66.
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What is the difference between a copy constructor and an
overloaded assignment operator?
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A copy constructor constructs a new object by using the
content of the argument object. An overloaded assignment operator assigns the
contents of an existing object to another existing object of the same class.
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67.
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What is a virtual destructor?
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The simple answer is that a virtual destructor is one that
is declared with the virtual attribute.
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68.
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What do you mean by Stack unwinding?
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It is a process during exception handling when the
destructor is called for all local objects between the place where the
exception was thrown and where it is caught.
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69.
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What is STL? and what are the components of stl?
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A collection of generic classes
and functions is called as Standard Template Library (STL).The stl components
are
- containers
- Algorithm
- Iterators
.
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70.
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What is a modifier?
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A modifier, also called a modifying function is a member
function that changes the value of at least one data member. In other words,
an operation that modifies the state of an object. Modifiers are also known
as mutators.
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71.
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What is an adaptor class or Wrapper class?
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A class that has no functionality of its own. Its member
functions hide the use of a third party software component or an object with
the non-compatible interface or a non-objectoriented implementation.
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72.
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What is a Null object?
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It is an object of some class whose purpose is to indicate
that a real object of that class does not exist. One common use for a null object
is a return value from a member function that is supposed to return an object
with some specified properties but cannot find such an object.
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73.
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What is class invariant?
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A class invariant is a condition that defines all valid
states for an object. It is a logical condition to ensure the correct working
of a class. Class invariants must hold when an object is created, and they
must be preserved under all operations of the class. In particular all class
invariants are both preconditions and post-conditions for all operations or
member functions of the class.
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74.
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What is the difference between the message and method?
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Message : Objects communicate by sending
messages to each other.A message is sent to invoke a method.
Method : Provides response to a message and it is an implementation
of an operation.
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75.
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How can we access protected and private members of a
class?
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In the case of members protected and private, these could
not be accessed from outside the same class at which they are declared. This
rule can be transgressed with the use of the friend keyword in a class, so we
can allow an external function to gain access to the protected and private
members of a class.
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76.
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What do you mean by late binding?
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Late binding refers to function calls that are not
resolved until run time. Virtual functions are used to achieve late binding.
When access is via a base pointer or reference, the virtual function actually
called is determined by the type of object pointed to by the pointer.
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77.
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What is virtual function?
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A virtual function is a member function that is declared
within a base class and redefined by a derived class .To create a virtual
function, the function declaration in the base class is preceded by the
keyword virtual.
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78.
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What do you mean by early binding?
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Early binding refers to the events that occur at compile
time. Early binding occurs when all information needed to call a function is
known at compile time. Examples of early binding include normal function
calls, overloaded function calls, and overloaded operators. The advantage of
early binding is efficiency.
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What is the difference between a NULL pointer and a void pointer?
Ans: A NULL pointer is a pointer of any type whose value is
zero. A void pointer is a pointer to an object of an unknown type, and is
guaranteed to have enough bits to hold a pointer to any object. A void pointer
is not guaranteed to have enough bits to point to a function (though in general
practice it does).
. What is difference between C++ and Java?
Ans: C++ has pointers Java does not.
Java is platform independent C++ is not.
Java has garbage collection C++ does not.
. What do you mean by multiple inheritance in C++ ?
Ans: Multiple inheritance is a feature in C++ by which one
class can be of different types. Say class teaching Assistant is inherited from
two classes say teacher and Student.
What do you mean by virtual
methods?
Ans: virtual methods are used to use the polymorphism feature
in C++. Say class A is inherited from class B. If we declare say function f()
as virtual in class B and override the same function in class A then at runtime
appropriate method of the class will be called depending upon the type of the
object.
What do you mean by static
methods?
Ans: By using the static method there is no need creating an
object of that class to use that method. We can directly call that method on
that class. For example, say class A has static function f(), then we can call
f() function as A.f(). There is no need of creating an object of class A.
How many ways are there to initialize an int with a constant?
Ans: Two.
There are two formats for initializers in C++ as shown in the example that
follows. The first format uses the traditional C notation. The second format
uses constructor notation.
int foo = 123;
int bar (123);
What is a constructor?
Ans: Constructor is a special member function of a class,
which is invoked automatically whenever an instance of the class is created. It
has the same name as its class.
What is destructor?
Ans: Destructor is a special member function of a class, which
is invoked automatically whenever an object goes out of the scope. It has the
same name as its class with a tilde character prefixed.
What is an explicit constructor?
Ans: 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.
What is the Standard Template Library?
Ans: A library of container templates approved by the ANSI
committee for inclusion in the standard C++ specification. A programmer who
then launches into a discussion of the generic programming model, iterators,
allocators, algorithms, and such, has a higher than average understanding of
the new technology that STL brings to C++ programming.
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