Question { 4111 }

why the memory allocated with new cant be freed using free()

Answer

new keyword does two things.
1) allocate memory using new operator
2) invokes the constructor.

so the allocated memory using new should be freed only by
delete which frees the memory by calling the destructor.

But free will not do these things.

Question { 4309 }

Difference between vector and array

Answer

Vector manages memory allocations, manages in the sense, it
provides constructor,copy constructor,assignment operator,
destructor etc. whereas array doesn't.

Question { 4041 }

Why is it so that we can have virtual constructors but we
cannot have virtual destructors?

Answer

We can have Virtual Destructor. We cannot have virtual
constructor, becoz, if the constructor is virtual, in
polymorphism, there may be a chance for the base class
constructor not to get executed. so the entire class will
not be available.

Question { 3459 }

what is namespace? what are the uses of namespace?

Answer

Namespaces allow to group entities like classes, objects
and functions under a name. This way the global scope can
be divided in "sub-scopes", each one with its own name.
The format of namespaces is:
namespace identifier
{
entities
}
Where identifier is any valid identifier and entities is
the set of classes, objects and functions that are included
within the namespace. For example:
namespace myNamespace
{
int a, b;
}
In this case, the variables a and b are normal variables
declared within a namespace called myNamespace. In order
to access these variables from outside the myNamespace
namespace we have to use the scope operator ::. For
example, to access the previous variables from outside
myNamespace we can write:
myNamespace::a
myNamespace::b

The functionality of namespaces is especially useful in the
case that there is a possibility that a global object or
function uses the same identifier as another one, causing
redefinition errors. For example:
// namespaces
#include
using namespace std;
namespace first
{
int var = 5;
}
namespace second
{
double var = 3.1416;
}
int main () {
cout << first::var << endl;
cout << second::var << endl;
return 0;
}
5
3.1416
In this case, there are two global variables with the same
name: var. One is defined within the namespace first
and the other one in second. No redefinition errors happen
thanks to namespaces.

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Question { Syntel, 5321 }

WHAT IS THE DIFFERENCE BETWEEN C++ AND VC++

Answer

VC++ uses all C++ features.VC++ has GUI and it is user
friendly.It has many programming features
likeWin32,MFC,ATL,ActiveX,DLL's etc.

Question { 3883 }

what are abstract classes and how they impliment , with
example

Answer

A class with atleast one pure virtual function is called
abstract class.It cant be instatiated.It can be used as a
base class for other classes. The class derived from an
abstract base class can be instantiated,provided it should
implement the abstract base class pure virtual function.