string s;
cout<< "Enter name: ";
cin >> s;

on running this i need:
Enter name: Tejesh Kinariwala
Tejesh Kinariwala

it is showing:
Enter name: Tejesh Kinariwala

so how to get the input till user hits return key, instead of breaking it at space

Well string class is defined so that it stops on reading a space or newline so alternatively you can do this :

char s[20];

This will read until it finds a \n' character and this will suffice your needs.

Use getline:

string s;
cout << "Enter some text: ";
getline(cin, s);
cout << "You typed: " << s << endl;