diff --git a/CMakeLists.txt b/CMakeLists.txt
index 58300ea..7d835c8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,12 +1,10 @@
 cmake_minimum_required(VERSION 3.0)
 
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_C_STANDARD 99)
 
-project(tiny_thread_demo LANGUAGES CXX)
+project(tiny_thread_pool LANGUAGES C)
 
-include_directories(src)
+add_library(tiny_pool tiny_pool.c)
+target_link_libraries(tiny_pool pthread)
 
-add_subdirectory(src)
-
-add_executable(demo demo.cc)
-target_link_libraries(demo tiny_pool)
+add_subdirectory(demo/cpp)
diff --git a/demo/cpp/CMakeLists.txt b/demo/cpp/CMakeLists.txt
new file mode 100644
index 0000000..82ff25b
--- /dev/null
+++ b/demo/cpp/CMakeLists.txt
@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.0)
+
+set(CMAKE_CXX_STANDARD 11)
+
+project(tiny_pool_demo_cpp LANGUAGES CXX)
+
+include_directories(../..)
+
+add_executable(demo_cpp demo.cc)
+target_link_libraries(demo_cpp tiny_pool)
diff --git a/demo.cc b/demo/cpp/demo.cc
similarity index 91%
rename from demo.cc
rename to demo/cpp/demo.cc
index 7c64aa8..25a6109 100644
--- a/demo.cc
+++ b/demo/cpp/demo.cc
@@ -20,7 +20,6 @@ public:
     auto submit(Func &&func, Args &&...args) -> std::future<decltype(func(args...))>;
 };
 
-
 template <typename Func, typename ...Args>
 auto TinyPool::submit(Func &&func, Args &&...args) -> std::future<decltype(func(args...))> {
     std::function<decltype(func(args...))()> wrap_func = std::bind(
@@ -37,7 +36,7 @@ auto TinyPool::submit(Func &&func, Args &&...args) -> std::future<decltype(func(
     return func_ptr->get_future();
 }
 
-/// -------------------------------- start test --------------------------------
+/// ------------------------------------ start test ------------------------------------
 
 #include <iostream>
 #include <unistd.h>
@@ -53,8 +52,6 @@ int test_func(char c) {
 }
 
 int main() {
-    std::cout << "tiny thread pool demo start" << std::endl;
-
     auto pool = TinyPool(3);
 
     auto f0 = pool.submit(test_func, '0');
@@ -86,7 +83,4 @@ int main() {
     printf("get future: %d\n", f1.get());
     printf("get future: %d\n", f9.get());
     printf("get future: %d\n", f7.get());
-
-    std::cout << "tiny thread pool demo exit" << std::endl;
-    return 0;
 }
diff --git a/main.c b/demo/demo.c
similarity index 100%
rename from main.c
rename to demo/demo.c
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
deleted file mode 100644
index f84f5d3..0000000
--- a/src/CMakeLists.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-cmake_minimum_required(VERSION 3.0)
-
-set(CMAKE_C_STANDARD 99)
-
-project(tiny_thread_pool LANGUAGES C)
-
-add_library(tiny_pool tiny_pool.c)
-target_link_libraries(tiny_pool pthread)
diff --git a/src/tiny_pool.c b/tiny_pool.c
similarity index 96%
rename from src/tiny_pool.c
rename to tiny_pool.c
index 508654f..e040f2f 100644
--- a/src/tiny_pool.c
+++ b/tiny_pool.c
@@ -9,11 +9,11 @@ void* run_pool_join(void *pool) { // single function for detach
 
 void tiny_pool_detach(pool_t *pool) {
     pthread_t tid;
-    pthread_create(&tid, NULL, run_pool_join, (void*)pool);
+    pthread_create(&tid, NULL, run_pool_join, (void*)pool); // new thread for detach
     pthread_detach(tid);
 }
 
-void free_tiny_pool(pool_t *pool) {
+void free_tiny_pool(pool_t *pool) { // free memory and destroy thread pool
     pthread_cond_destroy(&pool->without_busy_thread);
     pthread_cond_destroy(&pool->task_queue_not_empty);
     pthread_cond_destroy(&pool->task_queue_empty);
@@ -23,9 +23,9 @@ void free_tiny_pool(pool_t *pool) {
 }
 
 void tiny_pool_kill(pool_t *pool) {
-    if (pool->status > PREPARING) {
+    if (pool->status > PREPARING) { // threads are running
         for (uint32_t i = 0; i < pool->thread_num; ++i) {
-            pthread_cancel(pool->threads[i]);
+            pthread_cancel(pool->threads[i]); // kill sub threads
         }
     }
     free_tiny_pool(pool); // release thread pool
diff --git a/src/tiny_pool.h b/tiny_pool.h
similarity index 95%
rename from src/tiny_pool.h
rename to tiny_pool.h
index 6738362..32a6887 100644
--- a/src/tiny_pool.h
+++ b/tiny_pool.h
@@ -10,7 +10,7 @@
 #include <cstdbool>
 #endif
 
-/// This is a lightweight thread pool designed for linux. It is implemented in C language. Its
+/// This is a lightweight thread pool designed for Linux, it is implemented in C language. Its
 /// goal is to provide simple and stable services, so it does not provide functions such as priority
 /// and dynamic adjustment of the number of threads, and only provides the simplest threads pool
 /// implementation.
@@ -33,6 +33,9 @@
 ///              complete their tasks, the thread pool will be destroyed.
 ///
 /// These four life cycles must proceed sequentially: PREPARING -> RUNNING -> STOPPING -> EXITING
+///
+/// NOTE: The STOPPING and EXITING states are automatically managed by the thread pool, and users
+///       do not need to care about them.
 
 /// When using it, you need to use `tiny_pool_create` to create a thread pool first, and then use
 /// the `tiny_pool_submit` function to submit tasks to it. After the preparation is completed, use
@@ -60,7 +63,7 @@ enum pool_stage {
 typedef struct task_t {
     void (*entry)(void*); // function pointer of the task
     void *arg; // argument of task function
-    struct task_t *next; // the next task in the queue
+    struct task_t *next; // next task in the queue
 } task_t;
 
 typedef struct pool_t {