We've seen elementary output using the C++ I/O library. However, there is some additional boilerplate syntax that you will need to remember in order to use cout and the insertion operator without getting compiler errors.
using namespace std;
The fully qualified name of cout is std::cout. This is because
cout is defined in a C++ unit called a namespace. The particular
namespace used for many of the I/O facilities is 'std'.
The using clause above avoids your having to write the fully
qualified name and simply using 'cout'.