Do we have to explicitly define a default constructor when we define a copy constructor for a class?? Please give reasons.

eg: 

class A 
{
    int i;

    public:
           A(A& a)
           {
               i = a.i; //Ok this is corrected....
           }

           A() { } //Is this required if we write the above copy constructor??
};

Also, if we define any other parameterized constructor for a class other than the copy constructor, do we also have to define the default constructor?? Consider the above code without the copy constructor and replace it with 

A(int z)
{
    z.i = 10;
}

Alrite....After seeing the answers I wrote the following program.

#include <iostream>

using namespace std;

class X
{
    int i;

    public:
            //X();
            X(int ii);
            void print();
};

//X::X() { }

X::X(int ii)
{
    i = ii;
}


void X::print()
{
    cout<<"i = "<<i<<endl;
}

int main(void)
{
    X x(10);
  //X x1;
    x.print();
  //x1.print();
}

ANd this program seems to be working fine without the default constructor. Please explain why is this the case?? I am really confused with the concept.....

c++ constructor copy
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