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chethanhb  

 Profile Answers by chethanhb Questions by chethanhb

• Member Since Feb-2010 | Feb 25th, 2010

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I am one of the person who has pricked my head in understanding the above question. Let me explain in my way...

If you have virtual function or (let me take just "virtual" keyword as of now), it means that this member function can be redefined by derived class. When we have a virtual function in a class, it will have vtable (virtual table). This vtable will have the address of the virtual function which is defined in derived.
Now the point is, how you invoke the virtual function which is defined in derived class with the help of object of the class?
Once you create an object of class, vptr (virtual pointer) will be created. Which inturn will be pointing to the base address of the vtable. So now it is clear that you can invoke the virtual funtion of derived class only with an object that has created.
Now coming to virtual constructor,
If we make constructor as virtual in base, it means that it could be redefined in derived. Keep in mind that constructor is invoked during object creation (object is not created yet. still it is in the status "creating". Object will create only after executing constructor part code). Assume you are trying to create object of the class which has virtual constructor. During this process constructor of the class will be invoked. It looks for virtual keyword. Now it tries to look for virtual constructor in derived. But not possible bcz there is no vptr and no vtable avaibale at this point of time. So, when object is not created, then there is no vptr. If no vptr for this object, then how the consturtor of derived is invoked?. No address of this construtor will available in vtable.
Hence there is no point in having virtual constructor.

I believe that i have cleared your doubt.

Venkataramakrishna

• Mar 22nd, 2018

Whenever a class object is created this pointer is created just before initializing class constructor member values. If the constructor is virtual, you cannot create this pointer.

vikash tiwary

• May 11th, 2017

Virtual functions are used in order to invoke functions based on the type of object pointed by the pointer. But is not "invoked", it is called only once when it is declared. so, a constructor cannot be virtual.

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Structure: 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. Class: Class is a successor of Structure. By default all the members inside the class are private.

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sumitv  

 Profile Answers by sumitv Questions by sumitv

• Member Since Sep-2008 | Sep 4th, 2008

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Structure does support inheritance.

try out the following code.

#include<iostream>

using namespace std;

struct Base
{
    int A;
};

struct Derived:public Base
{
    int B;
    void display();
};

void Derived::display()
{
    cout<<endl<<"A = "<<A<<endl;
}

int main()
{
    Derived D;
    D.A = 111;
    D.display();
    getchar();
    return 0;
}

Try out private and protected inheritance as well. It works. :)

Regards,
Sumit

Sajeed Ullah

• Dec 2nd, 2016

All data members of the class is by default private,
Whereas all data members of structure is by default public.

Ashish

• Mar 24th, 2016

Beware, whatever is supported by a class is also supported by struct whether its inheritance, polymorphism, encapsulation, data hiding etc. etc. as of C++ 11. Only difference is, for a class default access specifier is private whereas for struct its public.

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Answered by: Kranthi Kiran

• Dec 2nd, 2006

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We cannot use a 'static variable' declared in one file and use it in file 2.Reason: The purpose of 'static' keyword is to retain the value betwwen the function and to restrict thescope of the variable to the file.When a variable is declared as static it will be given memory in global area portion of the process segments with the variable mname prefixed with the file namefor Example: static int k; implies it is stored as "filename.k" in global segment.so if you try to use it in another file the compiler finds the variable prefix and flags out an error.

Vineet Srivastava

• Nov 13th, 2015

Syntatically you cannot as static is meant for one file access only. But still if you want - you can do it by passing it by reference to another file through some function.

shreekant

• Nov 5th, 2015

Nice explained by Kalayama "We cant have two storage specifiers for a single Variable declaration. If one needs to use the variable in multiple files, then he needs to declare it has extern." Its simple thing.

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Venkataramakrishna

• Mar 22nd, 2018

Macro does not check for the data type. The inline function will check. You can enable or disable macros. in inline, depending on the requirement you can do this.

Naman

• Nov 14th, 2017

You pass some flags to the compiler to force inline or use always_inline attribute with GCC

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Abstraction is of the process of hiding unwanted details from the user. 

Ramya

• May 31st, 2013

Mechanism of exposing only the interface and hiding the implementation data from user.

mukrram ur rahman

• Dec 10th, 2012

Abstraction exactly involve the process of involving relevant things while ignoring the irrelevant things.

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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.  

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Answered by: hirma

• Sep 18th, 2005

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class is a userdefined datatype which consists of attributes(datamembers) and behavior(member functions).Bydefault the members of a class is private.

Nikita

• Jan 23rd, 2018

Class is a user define data type which contains the variable and function which r of two type private and public where the public class members can be accessed from any other class but the private cla...

Atul

• Dec 18th, 2017

Class is same as structure in C, but in Class we have functions

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hardikrlakhani

 Profile Answers by hardikrlakhani Questions by hardikrlakhani

• Jun 5th, 2011

c is program oriented language and c++ is a object oriented language

pammi_11

 Profile Answers by pammi_11 Questions by pammi_11

• May 31st, 2008

 c   is a procedural language. where as c++ is object oriented programming language.

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cclass base
{
public:
virtual void display(int i = 10)
{
cout

rohit suri

• Sep 11th, 2014

Base class display method will called

reddy-

• Apr 10th, 2013

Overriding function default argument takes more precedence ,Hence based class default argument 10 will be initialized to i.So i value holds 10 will be printed for this call with derived count statement.

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NikunjSingh

 Profile Answers by NikunjSingh Questions by NikunjSingh

• Feb 23rd, 2012

Destrcutors can be made private to stop user from creating objects on stack. One can still create objects on stack using a static function as member function. But if intention is not to let user crea...

mehulgala177

 Profile Answers by mehulgala177 Questions by mehulgala177

• Sep 22nd, 2011

YESSSS destructors can be private. Infact this concept is used in Singleton design pattern. So, outsiders cannot delete object of that class. It has to b deleted from the class itself. I know...I...

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ishanaditya

 Profile Answers by ishanaditya Questions by ishanaditya

• Sep 1st, 2014

There is nothing really wrong with C++ anymore. The few reservations I had personally have been fixed with the latest C++11 standard: - C++ wasnt really designed for writing multithreaded application...

robertgbjones

 Profile Answers by robertgbjones Questions by robertgbjones

• Aug 5th, 2014

Compared to what? C++ is a potentially low-level, close to the metal language, so potential for performance, though perhaps not as much as assembler, conversely its quite hard to learn, and now a big ...

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Bishoy

• Oct 20th, 2012

Local variables are stored in stack - each method have a stack frame (a fixed size of memory in the stack) that is allocated for local variables each time the method is called, and deallocated when th...

Ramanuj

• Oct 20th, 2012

Hi,

I have a query. The lifetime of the static variable is the entire program - if it is a local auto variable (i.e., not dynamically allocated), will it contribute to the peak memory ?

Regards,
Ramanu

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Public, protected and private are three access specifiers in C++. 1. Public data members and member functions are accessible outside the class.2. Protected data members and member functions are only available to derived classes.3. Private data members and member functions can’t be accessed outside the class. However there is an exception can be using friend classes.

ankit

• Jun 26th, 2015

Can we use protected specifier first than public than private in a class definition in c++ by making class

KomalUpadhyay

 Profile Answers by KomalUpadhyay Questions by KomalUpadhyay

• Nov 14th, 2009

Private Protected and Public all these are access specifiers.Private Data Members are only available inside classProtected Data Members are  only available inside class as well as in derived classes.Public Data members are available everywhere

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Why p++ is faster than p+1?

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sahasranaman  

 Profile Answers by sahasranaman Questions by sahasranaman

• Member Since Jul-2009 | Jul 1st, 2009

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p++ is faster because on compilation, it gets translated to three machine instructions, where as p=p+1 needs four machine instructions. All machine instructions take the same time.

For p++, the instructions are:
mov ax,
inc ax
mov,
ax

For p = p+ 1, the instructions would be,
mov ax,
mov bx, 1
add bx
mov,
ax

This is why p++ is faster than p+1

Mann2920

 Profile Answers by Mann2920 Questions by Mann2920

• Jan 24th, 2011

To perform?i+1?complier has to do:1-Addition i+12-Assignment i=result of additionWhile in case of i++Value is simply increased by 1so i++ is faster

Gargona

 Profile Answers by Gargona Questions by Gargona

• Feb 13th, 2010

Difference in assembler code:--$ diff -uN a2.S a.S--- ++p.S        2010-02-13 15:51:09.000000000 +0200+++ p+1.S 2010-02-13 15:50:30.000000000 +0200@@ -6,7 +6,6 @@&nb...

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harshitha

• Feb 8th, 2014

Ptr is a constant pointer to constant integer. Both the values cant be changed.
eg:
const int a=10;
const int *const ptr=&a;
int b=20;
const int *const ptr=&b;//error
a=25;//error

Jagadeesh Arikuti

• Jul 5th, 2012

Both are Constant
const int i=10;
const int * const ptr=&i;

You are not allowed to change int i are pointer ptr

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While doing inheritance in C++, one thing that is not inherited is what?

rohit suri

• Sep 11th, 2014

There are four things which r not inherited in c++
1>Constructor
2>Destructor
3>Assignment operator
4>copy constructor
5>Friend function

Johnny

• Jan 7th, 2014

Friend declarations.

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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.

charlie02

 Profile Answers by charlie02 Questions by charlie02

• Aug 9th, 2010

Friend function is a non-member function, which can?access the private member of a given class, only if it made as the friend of that class.

MCBod

 Profile Answers by MCBod Questions by MCBod

• Mar 31st, 2010

A friend function is a special function that has been granted access to the priovate members of a specific class. The class itself is responsible for declaring the friendship. It is nto affected by in...

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Krishna Kumar

• Sep 25th, 2018

There is three query for the above question, 1) Why reference object passed as parameter to the copy constructor? 2) Why pointer object is not passed as parameter to the copy constructor? 2) What r...

WinSound

 Profile Answers by WinSound Questions by WinSound

• May 31st, 2010

Copy constructor syntax:A(const A&) for the class "A"const - Indicates object passed as argument is not changed inside copy constructor so there may be 3 design possibliti...

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What is Static Polymorphism? Give its syntax and simple example.

rdl

• Dec 28th, 2014

The call to a function is resolved at compile time. Eg., function overloading and templates.

Youssef Arbach

• Dec 12th, 2014

Static polymorphism could be seen also with Templates, since the selection of the write function is done at compile time. Usually with inheritance (and call-by ref sure) polymorphism is dynamic, unless it is a call by-value, then there would be no morphism at all.

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sakshi

• Oct 4th, 2012

Code
span style="color: #ff0000;">"factorial of the no :"+f);
 
Console.ReadKey();
}

Anugya Singh

• Sep 4th, 2012

Code
#include<iostream.h>
#include<conio.h>
"Enter the Number whose factorial value is to be find 
""Fctorial is "<<f;
getch();
}

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SARAVANAN SIVAJI  

 Profile Answers by SARAVANAN SIVAJI Questions by SARAVANAN SIVAJI

• Member Since Aug-2007 | Aug 1st, 2007

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The main difference between C and C++ are:

1.  C is a procedural language whereas C++ is a non-procedural language.
2.  C gives importance to functions (methods) whereas C++ gives importance to both functions and data.
3.  C allows the data to flow around the functions freely whereas C++ wraps up the data and functions together, due to that datas were not allowed to flow around freely in C++.  This is said to be Encapsulation in C++
 

Other differences, ( actucally there is lot to mention......here are the two )

1.  C allows struct, union, and enum types to be declared in function prototypes, whereas C++ does not.

2.  A struct, union, or enum declaration in C++ declares an implicit typedef, while in C it does not

SARAVANAN SIVAJI

 Profile Answers by SARAVANAN SIVAJI Questions by SARAVANAN SIVAJI

• Aug 1st, 2007

One more point: we can include..........In C, the members in the struct, by default, public.In C++, the members in the class, by default, private.

SARAVANAN SIVAJI

 Profile Answers by SARAVANAN SIVAJI Questions by SARAVANAN SIVAJI

• Aug 1st, 2007

The main difference between C and C++ are:1.  C is a procedural language whereas C++ is a non-procedural language.2.  C gives importance to functions (methods) whereas C++ gives importance t...

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