diff --git a/src/FrontEnd/IntermediateCode/fe_icblock.py b/src/FrontEnd/IntermediateCode/fe_icblock.py
index d62fcf7..8ede3f5 100644
--- a/src/FrontEnd/IntermediateCode/fe_icblock.py
+++ b/src/FrontEnd/IntermediateCode/fe_icblock.py
@@ -32,7 +32,6 @@ class FEICBlock( FEICNode ):
     def __init__(self, parent:FEICNode=None):
         '''
         Constructor.
-
         '''
         super().__init__( [] )  ## content is an empty list (of FEICNode-s)
         self.parent = parent
diff --git a/src/FrontEnd/IntermediateCode/fe_icleaf.py b/src/FrontEnd/IntermediateCode/fe_icleaf.py
index 87bf614..6df7066 100644
--- a/src/FrontEnd/IntermediateCode/fe_icleaf.py
+++ b/src/FrontEnd/IntermediateCode/fe_icleaf.py
@@ -40,6 +40,13 @@ def __init__(self, content):
             content: a reference to the content opf this leaf
         '''
         super().__init__( content )
+    
+    #-------------------------------------------------------------------------
+    def set_parent(self, parent:FEICNode):
+        '''
+        Sets the parent of this node.
+        '''
+        pass
 
     #-------------------------------------------------------------------------
     def __iter__(self):
diff --git a/src/FrontEnd/IntermediateCode/fe_icnode.py b/src/FrontEnd/IntermediateCode/fe_icnode.py
index ffcb924..478cf58 100644
--- a/src/FrontEnd/IntermediateCode/fe_icnode.py
+++ b/src/FrontEnd/IntermediateCode/fe_icnode.py
@@ -39,6 +39,13 @@ def __init__(self, content=None):
         '''
         self.content = content
 
+    #-------------------------------------------------------------------------
+    def set_parent(self, parent:FEICNode):
+        '''
+        Sets the parent of this node.
+        '''
+        self.parent = parent
+
     #-------------------------------------------------------------------------
     def walk(self):
         '''
diff --git a/src/FrontEnd/IntermediateCode/fe_ictree.py b/src/FrontEnd/IntermediateCode/fe_ictree.py
index ac370b8..1583dda 100644
--- a/src/FrontEnd/IntermediateCode/fe_ictree.py
+++ b/src/FrontEnd/IntermediateCode/fe_ictree.py
@@ -24,11 +24,46 @@
 
 #=============================================================================
 from FrontEnd.IntermediateCode.fe_icblock import FEICBlock 
+from FrontEnd.IntermediateCode.fe_icnode  import FEICNode 
 
 
 #=============================================================================
-FEICTree = FEICBlock
-"""
-The class of Intermediate Code Trees.
-"""
+class FEICTree:
+    """
+    The class of Intermediate Code trees.
+    """
+
+    #-------------------------------------------------------------------------
+    def __init__(self):
+        '''
+        Constructor.
+        '''
+        self._root = FEICBlock()
+        self._current = self._root
+
+    #-------------------------------------------------------------------------
+    def __iadd__(self, ic_node:(FEICBlock,FEICNode)):
+        '''
+        Appends a new node into this block.
+        '''
+        ic_node.set_parent( self._current )
+        self._current += ic_node
+        if isinstance( ic_node, FEICBlock ):
+            self._current = ic_node
+
+    #-------------------------------------------------------------------------
+    def up(self):
+        '''
+        Goes back to parent block in IC Tree.
+        '''
+        self._current = self._current.parent
+
+    #-------------------------------------------------------------------------
+    def walk(self):
+        '''
+        Walks through this Intermediate Code tree.
+        Walk-through is depth-first implemented.
+        '''
+        self._root.walk()
+
 #=====   end of   FrontEnd.IntermediateCode.fe_ictree   =====#