diff --git a/struct-location/location.h b/struct-location/location.h
index 1c96eee..41ef140 100644
--- a/struct-location/location.h
+++ b/struct-location/location.h
@@ -1,3 +1,8 @@
+/*It is a tradition to use CPP tricks to avoid parsing the same header file more than once*/
+
+#ifndef LOCATION_H
+# define LOCATION_H
+
 /*use struct statement to define structure*/
 struct location {
   /*latitide like +052.26594*/
@@ -7,3 +12,5 @@ struct location {
 };
 
 struct location getLocation(char lat[11], char lon[10]);
+
+#endif /* LOCATION_H */
diff --git a/write-location-file/write-location-file.h b/write-location-file/write-location-file.h
index 09fe2ec..694de74 100644
--- a/write-location-file/write-location-file.h
+++ b/write-location-file/write-location-file.h
@@ -1 +1,8 @@
+/*It is a tradition to use CPP tricks to avoid parsing the same header file more than once*/
+
+#ifndef WRITE_LOCATION_FILE_H
+# define WRITE_LOCATION_FILE_H
+
 int write_location_file(char *lat, char *lon);
+
+#endif /* WRITE_LOCATION_FILE_H */