Added some comments

src/main/java/de/neemann/digital/core/ObservableValue.java

@@ -5,6 +5,12 @@ import de.neemann.digital.core.element.PinDescription;
 import de.neemann.digital.lang.Lang;
 
 /**
+ * Represents all signal values in the simulator.
+ * There are some setters to set the value. A value can be set to high z state.
+ * Only a complete bus can be set to high z state. It is not possible to set
+ * a single bit of a bus to high z state.
+ * Observers can observe this value to be notified if the value changes.
+ *
  * @author hneemann
  */
 public class ObservableValue extends Observable implements PinDescription {

src/main/java/de/neemann/digital/core/wiring/Delay.java

@@ -12,7 +12,9 @@ import de.neemann.digital.core.element.Keys;
 import static de.neemann.digital.core.element.PinInfo.input;
 
 /**
- * The Delay
+ * The Delay.
+ * Allows to delay a signal propagation by a certain amount of time.
+ * This time is given in units of gate delays.
  *
  * @author hneemann
  */

src/main/java/de/neemann/digital/core/wiring/bus/CommonBusValue.java

@@ -9,7 +9,8 @@ import java.io.File;
 import java.util.Arrays;
 
 /**
- * This observer is added to all outputs connected together
+ * This observer represents the common output value of several outputs connected together.
+ * Handles also the switches.
  */
 public final class CommonBusValue extends ObservableValue implements NodeInterface {
     private final BusModelStateObserver obs;

src/test/java/de/neemann/digital/integration/FileScanner.java

@@ -45,7 +45,7 @@ public class FileScanner {
             System.err.println("----> error in: " + e.f);
             e.e.printStackTrace();
         }
-        throw new Exception("errors testing files");
+        throw new Exception("errors testing files: " + errors.size());
     }
 
     private int scanIntern(File path) throws Exception {