doubt in objects creation

[abc1]

Can the objects in c++ created without using constructor?
For example in the following code
class value
{
int a;
public:
void getdata(int a)
{
cin>>a;
}
};
main()
{
value v;
v.getdata(1);
}
In the above code no constructor is defined.But the object 'v' is created.how?
If the object can be created without constructor then what is the use of constructor?please clear my doubts....

[Hippogriff]

Every class has some sort of constructor, if it is not directly specified by the user then a default constructor is used to handle the memory in class objects (you don't see all of this happening, it is done behind the scenes)

A constructor is useful to pass values into the class when an object is first created, for example if you were creating a game you would want to pass the health/speed/etc into the constructor when the object is first created to make those the default values.

[abc1]

@James2250,
that means object v is created by the default constructor.compiler creates default constructor?

[Hippogriff]

In this case, yep

[abc1]

@James2250,
Thank you

[meenakshipahwa]

Constructor is used to initialize the objects, not to create the objects.

[bluecoder]

Why are you passing the variable by value in the function.

void getdata(int a)
{
        cin>>a;
}

[ne555]

¿Why is it passing a variable at all?

[ceruleus]

the compiler creates 3 things for a class if you don't provide them. I always forget these 3 and I would love it if someone could recall... It's something like:
1- default constructor
2 - assignment operator
3 - virtual destructor? [edit] copy constructor ? [/edit]

[Disch]

1) default constructor
2) assignment operator
3) copy constructor
4) destructor

Note that a default constructor is provided only if you do not define any of your own constructors.

[meenakshipahwa]

while creation of objects, default constructor is automaticaly called.

value v;
or
value v = new value(); will do same work.........

here value() is default constructor

If anyone use only value v;
then this object will be initialized by other constructor

[LB]

value v;
or
value v = new value(); will do same work.........

Uh, no? The second line will not compile. If you meant this:
value v = value();
then it will only match value v; if the compiler optimizes it. Otherwise you create a temporary value object and then use the copy constructor to create v.

[sohguanh]

value v = new value(); will do same work.........

If it is a no-arg constructor the syntax should be value *v = new value;