diff --git a/course/4/CMakeLists.txt b/course/4/CMakeLists.txt
new file mode 100644
index 0000000..dccc9c6
--- /dev/null
+++ b/course/4/CMakeLists.txt
@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.12)
+
+project(HelloWorldProject VERSION 1.0.0)
+
+add_subdirectory(libs)
+add_subdirectory(app)
+
diff --git a/course/4/app/CMakeLists.txt b/course/4/app/CMakeLists.txt
new file mode 100644
index 0000000..1f4361c
--- /dev/null
+++ b/course/4/app/CMakeLists.txt
@@ -0,0 +1,3 @@
+add_executable(HelloApp main.cpp)
+
+target_link_libraries(HelloApp PRIVATE HelloLibrary)
\ No newline at end of file
diff --git a/course/4/app/main.cpp b/course/4/app/main.cpp
new file mode 100644
index 0000000..50cfeb3
--- /dev/null
+++ b/course/4/app/main.cpp
@@ -0,0 +1,8 @@
+#include <iostream>
+#include <hello/hello-library.hpp>
+
+int main()
+{
+    HelloLibrary::showHello();
+    return 0;
+}
\ No newline at end of file
diff --git a/course/4/build/.gitignore b/course/4/build/.gitignore
new file mode 100644
index 0000000..c96a04f
--- /dev/null
+++ b/course/4/build/.gitignore
@@ -0,0 +1,2 @@
+*
+!.gitignore
\ No newline at end of file
diff --git a/course/4/libs/CMakeLists.txt b/course/4/libs/CMakeLists.txt
new file mode 100644
index 0000000..c59a476
--- /dev/null
+++ b/course/4/libs/CMakeLists.txt
@@ -0,0 +1,9 @@
+add_library(
+    HelloLibrary
+    "${CMAKE_CURRENT_SOURCE_DIR}/hello/hello-library.hpp"
+    "${CMAKE_CURRENT_SOURCE_DIR}/hello/hello-library.cpp"
+)
+
+target_include_directories(HelloLibrary PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}")
+
+target_compile_definitions(HelloLibrary PRIVATE HELLO_VERSION=1.1)
\ No newline at end of file
diff --git a/course/4/libs/hello/hello-library.cpp b/course/4/libs/hello/hello-library.cpp
new file mode 100644
index 0000000..2170cbe
--- /dev/null
+++ b/course/4/libs/hello/hello-library.cpp
@@ -0,0 +1,7 @@
+#include "hello-library.hpp"
+#include <iostream>
+
+void HelloLibrary::showHello()
+{
+    std::cout<<"Hello world version: "<<HELLO_VERSION<<std::endl;
+}
\ No newline at end of file
diff --git a/course/4/libs/hello/hello-library.hpp b/course/4/libs/hello/hello-library.hpp
new file mode 100644
index 0000000..67ba62e
--- /dev/null
+++ b/course/4/libs/hello/hello-library.hpp
@@ -0,0 +1,9 @@
+#ifndef HELLO_LIBRARY_HPP
+#define HELLO_LIBRARY_HPP 1
+
+namespace HelloLibrary
+{
+    void showHello();
+}
+
+#endif
\ No newline at end of file