diff --git a/Inc/murasaki_2_ug.hpp b/Inc/murasaki_2_ug.hpp
index 3e55cab..079b508 100644
--- a/Inc/murasaki_2_ug.hpp
+++ b/Inc/murasaki_2_ug.hpp
@@ -21,6 +21,7 @@
  * \li \subpage ug_sec_3
  * \li \subpage ug_sec_4
  * \li \subpage ug_sec_5
+ * \li \subpage ug_sec_6
  *
  * For the easy-to-understand description, we assumes several things on the application skeleton which we are going to use Murasaki :
  * \li The application skeleton is generated by <a href= "http://www.st.com/ja/development-tools/stm32cubemx.html"> CubeMX </a>
@@ -362,4 +363,108 @@
  */
 
 
+
+/**
+ * @page ug_sec_6 Program flow
+ * @brief In this section, we see the program flow of a Murasaki application.
+ *
+ * Murasaki has 3 program flows. The start point of these flows are always inside
+ * CubeMX generated code. 2 out of 3 flows are for debugging. Only 1 flow have to be
+ * understood well by an application programmer.
+ *
+ * @li @subpage ug_sect_6_1
+ * @li @subpage ug_sect_6_2
+ * @li @subpage ug_sect_6_3
+ */
+
+/**
+ * @page ug_sect_6_1 Application flow
+ * @brief  The application program flow is the main flow of a Murasaki application.
+ *
+ * @details
+ * This program flow starts from the StartDefaultTask() in the Src/main.c.
+ * The StartDefaultTas() is a default and first task created by CubeMX.
+ * In the other words, this task is automatically created without configuration.
+ *
+ * From this function, two Murasaki function is called. One is InitPlatoform().
+ * The other is ExecPlatform(). Note that both function calls are inserted by
+ * installer. See @ref spg_6 of the @ref spg for details.
+ *
+ * @code
+ * void StartDefaultTask(void const * argument)
+ * {
+ *
+ *   // USER CODE BEGIN 5
+ *     InitPlatform();
+ *     ExecPlatform();
+ *   // Infinite loop
+ *   for(;;)
+ *   {
+ *     osDelay(1);
+ *   }
+ *   // USER CODE END 5
+ * }
+ * @endcode
+ *
+ * The InitPlatform() function is defined in the Src/murasaki_platform.cpp.
+ * Because the file extention is .cpp, the murasaki_platfrom.cpp is compiled
+ * by C++ compiler while the main.c is compiled by C compiler.
+ * This allows programmer uses C++ language. Thus, the InitPlatform() is the
+ * good place to initialize the class based variables.
+ *
+ * As the name suggests, InitPlatform() is where programmer initialize the
+ * platform variables murasaki::platform and murasaki::debugger.
+ * @code
+ * void InitPlatform()
+ * {
+ *    // UART device setting for console interface.
+ *    // On Nucleo, the port connected to the USB port of ST-Link is
+ *    // referred here.
+ *    murasaki::platform.uart_console = new murasaki::DebuggerUart(&huart3);
+ *    // UART is used for logging port.
+ *    // At least one logger is needed to run the debugger class.
+ *    murasaki::platform.logger = new murasaki::UartLogger(murasaki::platform.uart_console);
+ *    // Setting the debugger
+ *    murasaki::debugger = new murasaki::Debugger(murasaki::platform.logger);
+ *    // Set the debugger as AutoRePrint mode, for the easy operation.
+ *    murasaki::debugger->AutoRePrint();  // type any key to show history.
+
+
+ *    // For demonstration, one GPIO LED port is reserved.
+ *    // The port and pin names are fined by CubeMX.
+ *    murasaki::platform.led = new murasaki::BitOut(LD2_GPIO_Port, LD2_Pin);
+
+ *    // For demonstration of master and slave I2C
+ *    murasaki::platform.i2c_master = new murasaki::I2cMaster(&hi2c1);
+
+ *    murasaki::platform.sync_with_button = new murasaki::Synchronizer();
+
+ *    // For demonstration of FreeRTOS task.
+ *    murasaki::platform.task1 = new murasaki::Task(
+ *                                                  "Master",
+ *                                                  256,
+ *                                                  1,
+ *                                                  nullptr,
+ *                                                  &TaskBodyFunction
+ *                                                  );
+
+ *    // Following block is just for sample.
+
+ * }
+ * @endcode
+ *
+ */
+
+/**
+ * @page ug_sect_6_2 HAL Assertion flow
+ * @brief @ref murasaki::BitOut and murasaki::BitIn provides the GPIO functionality
+ */
+
+/**
+ * @page ug_sect_6_3 Sprious Interrupt flow
+ * @brief @ref murasaki::BitOut and murasaki::BitIn provides the GPIO functionality
+ */
+
+
+
 #endif /* MURASAKI_2_UG_HPP_ */