diff --git a/CMakeLists.txt b/CMakeLists.txt
index 801a9d0..2a75c5f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -51,25 +51,25 @@ include_directories(${PROJECT_SOURCE_DIR}/src ${PROJECT_SOURCE_DIR}/linenoise-ng
 # build
 add_executable(
   rpn
-  ${PROJECT_SOURCE_DIR}/src/main.cpp
-  ${PROJECT_SOURCE_DIR}/src/object.cpp
-  ${PROJECT_SOURCE_DIR}/src/mpreal-out.cpp
-  ${PROJECT_SOURCE_DIR}/src/program.cpp
-  ${PROJECT_SOURCE_DIR}/src/lexer.cpp
-  ${PROJECT_SOURCE_DIR}/src/input.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-branch.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-complex.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-general.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-logs.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-program.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-real.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-stack.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-store.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-string.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-test.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-test-framework.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-time.cpp
-  ${PROJECT_SOURCE_DIR}/src/rpn-trig.cpp
+  ${PROJECT_SOURCE_DIR}/src/main.cc
+  ${PROJECT_SOURCE_DIR}/src/object.cc
+  ${PROJECT_SOURCE_DIR}/src/mpreal-out.cc
+  ${PROJECT_SOURCE_DIR}/src/program.cc
+  ${PROJECT_SOURCE_DIR}/src/lexer.cc
+  ${PROJECT_SOURCE_DIR}/src/input.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-branch.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-complex.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-general.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-logs.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-program.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-real.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-stack.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-store.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-string.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-test.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-test-framework.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-time.cc
+  ${PROJECT_SOURCE_DIR}/src/rpn-trig.cc
   ${PROJECT_SOURCE_DIR}/linenoise-ng/src/ConvertUTF.cpp
   ${PROJECT_SOURCE_DIR}/linenoise-ng/src/linenoise.cpp
   ${PROJECT_SOURCE_DIR}/linenoise-ng/src/wcwidth.cpp
diff --git a/src/input.cpp b/src/input.cc
similarity index 99%
rename from src/input.cpp
rename to src/input.cc
index 7c84f5b..c9c50bf 100644
--- a/src/input.cpp
+++ b/src/input.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "input.hpp"
+#include "input.h"
 
 #include <cstring>
 
diff --git a/src/input.hpp b/src/input.h
similarity index 100%
rename from src/input.hpp
rename to src/input.h
diff --git a/src/lexer.cpp b/src/lexer.cc
similarity index 99%
rename from src/lexer.cpp
rename to src/lexer.cc
index 98b4ab8..79cee56 100644
--- a/src/lexer.cpp
+++ b/src/lexer.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "lexer.hpp"
+#include "lexer.h"
 
 bool Lexer::Analyse(string& entry, map<string, ReservedWord>& keywords, vector<SynElement>& elements,
                   vector<SynError>& errors) {
diff --git a/src/lexer.hpp b/src/lexer.h
similarity index 99%
rename from src/lexer.hpp
rename to src/lexer.h
index 532ee23..e31ba0a 100644
--- a/src/lexer.hpp
+++ b/src/lexer.h
@@ -11,7 +11,7 @@ using mpfr::mpreal;
 #include <vector>
 using std::map, std::string, std::vector;
 
-#include "object.hpp"
+#include "object.h"
 
 class Lexer {
  public:
diff --git a/src/main.cpp b/src/main.cc
similarity index 98%
rename from src/main.cpp
rename to src/main.cc
index 9f5d2b5..374b0f9 100644
--- a/src/main.cpp
+++ b/src/main.cc
@@ -9,8 +9,8 @@
 using std::cerr;
 
 // internal includes
-#include "input.hpp"
-#include "program.hpp"
+#include "input.h"
+#include "program.h"
 
 /// @brief actions to be done at rpn exit
 ///
diff --git a/src/mpreal-out.cpp b/src/mpreal-out.cc
similarity index 99%
rename from src/mpreal-out.cpp
rename to src/mpreal-out.cc
index 6b71028..dfb5d4b 100644
--- a/src/mpreal-out.cpp
+++ b/src/mpreal-out.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "mpreal-out.hpp"
+#include "mpreal-out.h"
 
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
 #define MAX(h, i) ((h) > (i) ? (h) : (i))
diff --git a/src/mpreal-out.hpp b/src/mpreal-out.h
similarity index 100%
rename from src/mpreal-out.hpp
rename to src/mpreal-out.h
diff --git a/src/object.cpp b/src/object.cc
similarity index 87%
rename from src/object.cpp
rename to src/object.cc
index 840266e..36deefd 100644
--- a/src/object.cpp
+++ b/src/object.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "object.hpp"
+#include "object.h"
 
 // number statics
 Number::mode_enum Number::mode = Number::kDefaultMode;
diff --git a/src/object.hpp b/src/object.h
similarity index 98%
rename from src/object.hpp
rename to src/object.h
index 68eff2e..bf56f39 100644
--- a/src/object.hpp
+++ b/src/object.h
@@ -1,7 +1,7 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#ifndef SRC_OBJECT_HPP_
-#define SRC_OBJECT_HPP_
+#ifndef SRC_OBJECT_H_
+#define SRC_OBJECT_H_
 
 #include <mpreal.h>
 using mpfr::mpreal;
@@ -12,7 +12,7 @@ using mpfr::mpreal;
 #include <string>
 using std::complex, std::ostream, std::string, std::stringstream;
 
-#include "mpreal-out.hpp"
+#include "mpreal-out.h"
 
 // definitions for objects
 ///
@@ -212,4 +212,4 @@ struct Branch : Object {
     string value;
 };
 
-#endif  // SRC_OBJECT_HPP_
+#endif  // SRC_OBJECT_H_
diff --git a/src/program.cpp b/src/program.cc
similarity index 99%
rename from src/program.cpp
rename to src/program.cc
index 0276800..12e5ef4 100644
--- a/src/program.cpp
+++ b/src/program.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 //< language reserved keywords (allowed types are kKeyword, kBranch or kUndef)
 vector<program::keyword_t> program::keywords_{
diff --git a/src/program.hpp b/src/program.h
similarity index 99%
rename from src/program.hpp
rename to src/program.h
index 1df080f..cfe5827 100644
--- a/src/program.hpp
+++ b/src/program.h
@@ -14,9 +14,9 @@ using namespace std;
 using mpfr::mpreal;
 
 // internal includes
-#include "lexer.hpp"
-#include "object.hpp"
-#include "stack.hpp"
+#include "lexer.h"
+#include "object.h"
+#include "stack.h"
 
 //< program class: the class containing a string parser, all the programs keywords, a stack for running the program
 class program : public deque<Object*>, public Lexer {
diff --git a/src/rpn-branch.cpp b/src/rpn-branch.cc
similarity index 99%
rename from src/rpn-branch.cpp
rename to src/rpn-branch.cc
index 133c2f8..e72d0cf 100644
--- a/src/rpn-branch.cpp
+++ b/src/rpn-branch.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief if keyword (branch) implementation
 ///
diff --git a/src/rpn-complex.cpp b/src/rpn-complex.cc
similarity index 99%
rename from src/rpn-complex.cpp
rename to src/rpn-complex.cc
index c0b01e5..55d3aed 100644
--- a/src/rpn-complex.cpp
+++ b/src/rpn-complex.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief re keyword implementation
 /// the result is stacked on current program stack
diff --git a/src/rpn-general.cpp b/src/rpn-general.cc
similarity index 99%
rename from src/rpn-general.cpp
rename to src/rpn-general.cc
index abe720e..7437f8f 100644
--- a/src/rpn-general.cpp
+++ b/src/rpn-general.cc
@@ -6,7 +6,7 @@
 using std::cout, std::string, std::pair;
 
 #include "linenoise.h"
-#include "program.hpp"
+#include "program.h"
 #include "version.h"
 
 // description
diff --git a/src/rpn-logs.cpp b/src/rpn-logs.cc
similarity index 99%
rename from src/rpn-logs.cpp
rename to src/rpn-logs.cc
index 1568dd8..379ad79 100644
--- a/src/rpn-logs.cpp
+++ b/src/rpn-logs.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief e keyword implementation
 ///
diff --git a/src/rpn-program.cpp b/src/rpn-program.cc
similarity index 99%
rename from src/rpn-program.cpp
rename to src/rpn-program.cc
index 7bc7006..c4d0199 100644
--- a/src/rpn-program.cpp
+++ b/src/rpn-program.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief find variable by its name in local heap, successive parents heaps, global heap
 ///
diff --git a/src/rpn-real.cpp b/src/rpn-real.cc
similarity index 99%
rename from src/rpn-real.cpp
rename to src/rpn-real.cc
index 53750c3..93f9901 100644
--- a/src/rpn-real.cpp
+++ b/src/rpn-real.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief + keyword implementation
 ///
diff --git a/src/rpn-stack.cpp b/src/rpn-stack.cc
similarity index 99%
rename from src/rpn-stack.cpp
rename to src/rpn-stack.cc
index f4e3d1d..92b2892 100644
--- a/src/rpn-stack.cpp
+++ b/src/rpn-stack.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief swap keyword implementation
 ///
diff --git a/src/rpn-store.cpp b/src/rpn-store.cc
similarity index 99%
rename from src/rpn-store.cpp
rename to src/rpn-store.cc
index e387703..3e9c316 100644
--- a/src/rpn-store.cpp
+++ b/src/rpn-store.cc
@@ -1,7 +1,7 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "input.hpp"
-#include "program.hpp"
+#include "input.h"
+#include "program.h"
 
 /// @brief sto keyword implementation
 ///
diff --git a/src/rpn-string.cpp b/src/rpn-string.cc
similarity index 99%
rename from src/rpn-string.cpp
rename to src/rpn-string.cc
index 69199cf..83b3340 100644
--- a/src/rpn-string.cpp
+++ b/src/rpn-string.cc
@@ -2,7 +2,7 @@
 
 #include <fcntl.h>
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief ->str keyword implementation
 ///
diff --git a/src/rpn-test-framework.cpp b/src/rpn-test-framework.cc
similarity index 99%
rename from src/rpn-test-framework.cpp
rename to src/rpn-test-framework.cc
index 7e68476..f0e4742 100644
--- a/src/rpn-test-framework.cpp
+++ b/src/rpn-test-framework.cc
@@ -3,7 +3,7 @@
 #include <string>
 using std::string;
 
-#include "program.hpp"
+#include "program.h"
 #include "version.h"
 
 // foreground colors
diff --git a/src/rpn-test.cpp b/src/rpn-test.cc
similarity index 99%
rename from src/rpn-test.cpp
rename to src/rpn-test.cc
index 2ce25a5..fe610b0 100644
--- a/src/rpn-test.cpp
+++ b/src/rpn-test.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief compared 2 strings on top of the stack_
 ///
diff --git a/src/rpn-time.cpp b/src/rpn-time.cc
similarity index 98%
rename from src/rpn-time.cpp
rename to src/rpn-time.cc
index 84e9e71..f763dba 100644
--- a/src/rpn-time.cpp
+++ b/src/rpn-time.cc
@@ -2,7 +2,7 @@
 
 #include <ctime>
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief time keyword implementation
 ///
diff --git a/src/rpn-trig.cpp b/src/rpn-trig.cc
similarity index 99%
rename from src/rpn-trig.cpp
rename to src/rpn-trig.cc
index 0fa99f1..d31ceb3 100644
--- a/src/rpn-trig.cpp
+++ b/src/rpn-trig.cc
@@ -1,6 +1,6 @@
 // Copyright (c) 2014-2022 Louis Rubet
 
-#include "program.hpp"
+#include "program.h"
 
 /// @brief pi keyword implementation
 ///
diff --git a/src/stack.hpp b/src/stack.h
similarity index 98%
rename from src/stack.hpp
rename to src/stack.h
index abc216e..96cf050 100644
--- a/src/stack.hpp
+++ b/src/stack.h
@@ -9,7 +9,7 @@
 #include <algorithm>
 using std::deque, std::map, std::string;
 
-#include "object.hpp"
+#include "object.h"
 
 /// @brief stack object, parens of program, storing execution stack values or programs
 ///