diff --git a/src/Color.h b/src/Color.h
index 54b6e88..93172d7 100644
--- a/src/Color.h
+++ b/src/Color.h
@@ -4,6 +4,11 @@
 static const Color black = Color(0, 0, 0);
 static const Color white = Color(255, 255, 255);
 
+/**
+ * color values represented as rgb values.
+ * @author Johannes Theiner
+ * @since 0.1.0
+ */
 class Color {
 
 private:
diff --git a/src/EventType.h b/src/EventType.h
index 52e07e0..6daa1ea 100644
--- a/src/EventType.h
+++ b/src/EventType.h
@@ -2,6 +2,7 @@
 #define LIBRARY_EVENTTYPE_H
 
 /**
+ * types of events.
  * @since 0.1.0
  * @uthor Johannes Theiner
  */
diff --git a/src/GraphicMode.h b/src/GraphicMode.h
index 77f82c1..d447ee8 100644
--- a/src/GraphicMode.h
+++ b/src/GraphicMode.h
@@ -1,6 +1,11 @@
 #ifndef LIBRARY_GRAPHICMODE_H
 #define LIBRARY_GRAPHICMODE_H
 
+/**
+ * all possible graphics modes.
+ * @author Johannes Theiner
+ * @since 0.1.0
+ */
 enum GraphicMode {
     Text = 1,
     TwoColors = 2,
diff --git a/src/internal.h b/src/internal.h
index 5e3b072..e67ce89 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -5,25 +5,42 @@
 #include "KeyCode.h"
 #include "LayoutVersion.h"
 
-//TODO: documentation
-
+/**
+ * set layout version.
+ * @param newValue new layout version number.
+ */
 void setLayoutVersion(LayoutVersion newValue);
 
-void setTriggerReset(int newValue);
-
+/**
+ * set characters per line for current font.
+ * @param newValue characters per line.
+ */
 void setCharactersPerLine(int newValue);
 
+/**
+ * set characters per row for current font.
+ * @param newValue
+ */
 void setCharactersPerRow(int newValue);
 
 /**
  * call a specific event.
  * @param type
- * @return true if there is a handler registere
+ * @return true if there is a handler registered.
  */
 bool callEvent(EventType type);
 
+/**
+ * set mouse position to x,y value.
+ * @param x x coordinate
+ * @param y y coordinate
+ */
 void setMousePosition(int x, int y);
 
+/**
+ * register pressed button.
+ * @param keyCode pressed key.
+ */
 void buttonPressed(KeyCode keyCode);
 
 // Shared Memory Layout