WAP to concatenate 2 strings using constructor & destructor ( dynamic constructor ).

This program:- 
1. Inputs 2 strings by user.
2.Concatenates them using dynamic constructor. 
We have defined a class String which has String constructor performing concatenation. Here we have input the 2 strings as 'Hello' & 'World'.

CODE:---

#include<iostream>
#include<string.h>
using namespace std;
class String
{
char *name;
int length;
public:
String()
{
length=0;
name= new char[length+1];
}
String(char *s)
{
length=strlen(s);
name= new char[length+1];
strcpy(name,s);
}
void display()
{
cout<<name<<endl;
}
void join(String &a,String &b)
{
length=a.length+b.length;
delete name;
name= new char[length+1];
strcpy(name,a.name);
strcat(name,b.name);
}
};
int main()
{
String name1("Hello"),name2("World"),s1;
s1.join(name1,name2);
name1.display();
name2.display();
s1.display();
}