diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6e88a8a..b56152d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,10 +16,14 @@ cmake_minimum_required(VERSION 2.8.12)
 project(CSerialPort LANGUAGES CXX)
 
 # set output directory
-if (CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
-    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
-    set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
-    set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
+if(NOT CMAKE_RUNTIME_OUTPUT_DIRECTORY)
+	set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)					
+endif()
+if(NOT CMAKE_LIBRARY_OUTPUT_DIRECTORY)
+	set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)					
+endif()
+if(NOT CMAKE_ARCHIVE_OUTPUT_DIRECTORY)
+	set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)					
 endif()
 
 # set build tpye
diff --git a/bindings/c/CMakeLists.txt b/bindings/c/CMakeLists.txt
index 753f963..da9c202 100644
--- a/bindings/c/CMakeLists.txt
+++ b/bindings/c/CMakeLists.txt
@@ -19,22 +19,42 @@ add_definitions(-DCSERIALPORT_DEBUG) # CSerialPort Debug Mode
 add_definitions(-DCSERIALPORT_BINDING_LANGUAGE=C) # CSerialPort Binding Language
 
 # set output directory
-set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
-set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
-set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
+if(NOT CMAKE_RUNTIME_OUTPUT_DIRECTORY)
+	set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)					
+endif()
+if(NOT CMAKE_LIBRARY_OUTPUT_DIRECTORY)
+	set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)					
+endif()
+if(NOT CMAKE_ARCHIVE_OUTPUT_DIRECTORY)
+	set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)					
+endif()
 
 # cserialport files
 set(CSerialPortRootPath "${CMAKE_CURRENT_SOURCE_DIR}/../..")
-include_directories(${CSerialPortRootPath}/include)
-list(APPEND CSerialPortSourceFiles ${CSerialPortRootPath}/src/SerialPort.cpp ${CSerialPortRootPath}/src/SerialPortBase.cpp ${CSerialPortRootPath}/src/SerialPortInfo.cpp ${CSerialPortRootPath}/src/SerialPortInfoBase.cpp)
+list(APPEND CSerialPortSourceFiles 
+    ${CSerialPortRootPath}/src/SerialPort.cpp 
+    ${CSerialPortRootPath}/src/SerialPortBase.cpp 
+    ${CSerialPortRootPath}/src/SerialPortInfo.cpp 
+    ${CSerialPortRootPath}/src/SerialPortInfoBase.cpp
+)
 if (WIN32)
-    list(APPEND CSerialPortSourceFiles ${CSerialPortRootPath}/src/SerialPortInfoWinBase.cpp ${CSerialPortRootPath}/src/SerialPortWinBase.cpp)
-    list(APPEND CSerialPortSourceFiles ${CSerialPortRootPath}/lib/version.rc)
+    list(APPEND CSerialPortSourceFiles 
+        ${CSerialPortRootPath}/src/SerialPortInfoWinBase.cpp 
+        ${CSerialPortRootPath}/src/SerialPortWinBase.cpp
+    )
+    list(APPEND CSerialPortSourceFiles 
+        ${CSerialPortRootPath}/lib/version.rc
+    )
 elseif (UNIX)
-    list(APPEND CSerialPortSourceFiles ${CSerialPortRootPath}/src/SerialPortInfoUnixBase.cpp ${CSerialPortRootPath}/src/SerialPortUnixBase.cpp)
+    list(APPEND CSerialPortSourceFiles 
+        ${CSerialPortRootPath}/src/SerialPortInfoUnixBase.cpp 
+        ${CSerialPortRootPath}/src/SerialPortUnixBase.cpp
+    )
 endif ()
 
 add_library(${PROJECT_NAME} SHARED cserialport.cpp ${CSerialPortSourceFiles})
+target_include_directories(cserialport PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+target_include_directories(cserialport PRIVATE ${CSerialPortRootPath}/include)
 
 if (WIN32)
     target_link_libraries(${PROJECT_NAME} user32 advapi32 setupapi)
@@ -44,7 +64,12 @@ elseif (APPLE)
     target_link_libraries(${PROJECT_NAME} ${FOUNDATION_LIBRARY} ${IOKIT_LIBRARY})
 elseif (UNIX)
     target_link_libraries(${PROJECT_NAME} pthread)
+    if(CMAKE_COMPILER_IS_GNUCC)
+        target_link_libraries(${PROJECT_NAME} rt)
+    endif()
 endif ()
 
 # example
-add_subdirectory(example)
\ No newline at end of file
+if (CSERIALPORT_BUILD_EXAMPLES)
+    add_subdirectory(example)
+endif ()
diff --git a/bindings/c/cserialport.cpp b/bindings/c/cserialport.cpp
index 3ce249a..c5d32ba 100644
--- a/bindings/c/cserialport.cpp
+++ b/bindings/c/cserialport.cpp
@@ -68,7 +68,7 @@ void CSerialPortAvailablePortInfosMalloc(SerialPortInfoArray *portInfoArray)
     }
     else
     {
-        portInfoArray->portInfo = NULL;
+        portInfoArray->portInfo = nullptr;
     }
 }
 
@@ -77,12 +77,12 @@ void CSerialPortAvailablePortInfosFree(struct SerialPortInfoArray *portInfoArray
     if (portInfoArray)
     {
         delete[] portInfoArray->portInfo;
-        portInfoArray->portInfo = NULL;
+        portInfoArray->portInfo = nullptr;
         portInfoArray->size = 0;
     }
 }
 
-i_handle_t CSerialPortMalloc()
+i_handle_t CSerialPortMalloc(void)
 {
     return reinterpret_cast<i_handle_t>(new itas109::CSerialPort());
 }
@@ -93,7 +93,7 @@ void CSerialPortFree(i_handle_t handle)
     if (pCSP)
     {
         delete pCSP;
-        pCSP = NULL;
+        pCSP = nullptr;
     }
 }
 
diff --git a/bindings/c/cserialport.h b/bindings/c/cserialport.h
index 6ada791..37f86e0 100644
--- a/bindings/c/cserialport.h
+++ b/bindings/c/cserialport.h
@@ -81,7 +81,7 @@ extern "C"
 
     C_DLL_EXPORT void CSerialPortAvailablePortInfosFree(struct SerialPortInfoArray *portInfoArray);
 
-    C_DLL_EXPORT i_handle_t CSerialPortMalloc();
+    C_DLL_EXPORT i_handle_t CSerialPortMalloc(void);
 
     C_DLL_EXPORT void CSerialPortFree(i_handle_t handle);