few, FINALLY BUILDED

cpp/hello-world/hello_world.h

@@ -0,0 +1,22 @@
+// This is an include guard.
+// You could alternatively use '#pragma once'
+// See https://en.wikipedia.org/wiki/Include_guard
+#if !defined(HELLO_WORLD_H)
+#define HELLO_WORLD_H
+
+// Include the string header so that we have access to 'std::string'
+#include <string>
+
+// Declare a namespace for the function(s) we are exporting.
+// https://en.cppreference.com/w/cpp/language/namespace
+namespace hello_world {
+
+// Declare the 'hello()' function, which takes no arguments and returns a
+// 'std::string'. The function itself is defined in the hello_world.cpp source
+// file. Because it is inside of the 'hello_world' namespace, it's full name is
+// 'hello_world::hello()'.
+std::string hello();
+
+}  // namespace hello_world
+
+#endif