Why is #include <string> needed for string objects but not string literals?

Question

How come when using the string object for variables and parameters you need to have #include <string> , but you don't need it for string literals? For example, you can say cout << "This is a string literal"; without #include <string> .

I am learning C++ using a Deitel Brothers book and came up with this question when learning character arrays.

Answer 1

A string literal is not a std::string object, it's an array of const char .
"This is a string literal" has the type const char[25] .

In most situations – including this one – an array implicitly decays into a pointer to its first element, and there is an operator<< overload for const char* .

It's pretty confusing that "string" means several different things in C++, but after a while (and pulling of hair and gnashing of teeth) the intended meaning will be clear from context.

Answer 2

A string literal like "This is a string literal" is of type const char[25] , not of type std::string . Statement cout << "This is a string literal" actually calls operator <<(ostream&, const char*) , and the string literal parameter decays to type const char* . There isn't any std::string involved in this case.