diff --git a/bintree.c b/bintree.c
index 294ac6d..1b8aa4c 100644
--- a/bintree.c
+++ b/bintree.c
@@ -66,15 +66,21 @@ TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFc
 // push the top node and push all its left nodes.
 void *nextTreeData(TreeNode *root)
 {
+  if(root == NULL)
+    {
 
+
+    }
+  stackNode.top(root);
 }
 
 // Releases all memory resources (including data copies).
 void clearTree(TreeNode *root)
 {
     if (root == NULL)
+      {
         return;
-
+      }
     // Erst linken Knoten löschen
     clearTree(root->left);
 
diff --git a/stack.c b/stack.c
index e3a90d4..916ac51 100644
--- a/stack.c
+++ b/stack.c
@@ -10,7 +10,17 @@
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data)
 {
-
+    if(stack && data){
+      StackNode *t = (StackNode *)malloc(sizeof(StackNode));
+      if(!t)
+        {
+        return NULL; //Speicherfehler
+        }
+      t->prev = stack;
+      t->data = data;
+      return t;
+      }
+    return NULL;
 }
 
 // Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
diff --git a/stack.h b/stack.h
index a2b8a17..e962b2b 100644
--- a/stack.h
+++ b/stack.h
@@ -10,8 +10,7 @@ The latest element is taken from the stack. */
 //TODO: passenden Datentyp als struct anlegen
 typedef{
   int* data;
-  unsigned int *fol;
-  unsigned int *prev;
+  struct StackNode *prev;
   }StackNode;
 
 // Pushes data as pointer onto the stack.