Fir what do u use "string" headerfile?

Answer 1

<string> includes the string class, which is used for manipulation of string objects.

http://en.cppreference.com/w/cpp/header/string

Some compilers automatically add the <string> header for you, when you use a string variable. However, it is better to explicitly include the header if you will be using strings. VS2017, for example does not overload << for string variables in the output stream if <string> is not included.

Answer 2

strings..

i.e
string someText { "This is a string" };