cin does not read characters after space. Use
cin.getline() instead of
cin if you want to read more than one word. Also sync the input stream.
#include <iostream.h>
#include <conio.h>
#include <string.h>
void main()
{
clrscr();
char first[20];
char seond[20];
cin.sync();
cout<<"Enter string";
cin.getline(first,20);
strcpy(seond,first);
cout<<seond;
getch();
}