diff --git a/P04_Modularisieren_von_C_Code/work/modularize/src/read.c b/P04_Modularisieren_von_C_Code/work/modularize/src/read.c
index 05c2a20..2b998bd 100644
--- a/P04_Modularisieren_von_C_Code/work/modularize/src/read.c
+++ b/P04_Modularisieren_von_C_Code/work/modularize/src/read.c
@@ -13,14 +13,7 @@
  */
 // begin students to add code for task 4.1
 #include <stdio.h>
-#define EOL 10
-#define PARSE_ERROR -1
-#define READ_ERROR -2
-#define ASCII_SPACE 32
-#define ASCII_DIGIT_0 48
-#define ASCII_DIGIT_9 57
-#define NO_POS -1
-#define BUFFERSIZE 10
+#include "read.h"
 int getInt(int maxResult) {
     char buffer[BUFFERSIZE] = {0};
     int result = 0;
diff --git a/P04_Modularisieren_von_C_Code/work/modularize/src/read.h b/P04_Modularisieren_von_C_Code/work/modularize/src/read.h
index 16187fe..a0b29d8 100644
--- a/P04_Modularisieren_von_C_Code/work/modularize/src/read.h
+++ b/P04_Modularisieren_von_C_Code/work/modularize/src/read.h
@@ -12,5 +12,19 @@
  * @brief Lab implementation
  */
 // begin students to add code for task 4.1
+#ifndef READ_H
+#define READ_H
 
+#define EOL 10
+#define PARSE_ERROR -1
+#define READ_ERROR -2
+#define ASCII_SPACE 32
+#define ASCII_DIGIT_0 48
+#define ASCII_DIGIT_9 57
+#define NO_POS -1
+#define BUFFERSIZE 10
+
+int getInt(int maxResult);
+
+#endif
 // end students to add code
diff --git a/P04_Modularisieren_von_C_Code/work/modularize/src/rectang.h b/P04_Modularisieren_von_C_Code/work/modularize/src/rectang.h
index 16187fe..5939468 100644
--- a/P04_Modularisieren_von_C_Code/work/modularize/src/rectang.h
+++ b/P04_Modularisieren_von_C_Code/work/modularize/src/rectang.h
@@ -12,5 +12,11 @@
  * @brief Lab implementation
  */
 // begin students to add code for task 4.1
+#ifndef RECTANG_H
+#define RECTANG_H
+
+int Rectangular(int a, int b, int c);
+
+#endif
 
 // end students to add code