diff --git a/Makefile.am b/Makefile.am
index 02ebadd..dfd86be 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -7,6 +7,9 @@ libcwSRC +=                      src/libcw/cwCommonImpl.cpp src/libcw/cwMem.cpp
 libcwHDR += src/libcw/cwString.h   src/libcw/cwMath.h   src/libcw/cwVectOps.h src/libcw/cwMtx.h    src/libcw/cwVariant.h
 libcwSRC += src/libcw/cwString.cpp src/libcw/cwMath.cpp                       src/libcw/cwMtx.cpp  src/libcw/cwVariant.cpp
 
+libcwHDR += src/libcw/cwB23Tree.h
+libcwSRC += src/libcw/cwB23Tree.cpp
+
 libcwHDR += src/libcw/cwFileSys.h   src/libcw/cwText.h   src/libcw/cwFile.h    src/libcw/cwTime.h   src/libcw/cwLex.h   src/libcw/cwNumericConvert.h 
 libcwSRC += src/libcw/cwFileSys.cpp src/libcw/cwText.cpp src/libcw/cwFile.cpp  src/libcw/cwTime.cpp src/libcw/cwLex.cpp
 
diff --git a/cwB23Tree.cpp b/cwB23Tree.cpp
new file mode 100644
index 0000000..d028cf9
--- /dev/null
+++ b/cwB23Tree.cpp
@@ -0,0 +1,47 @@
+#include "cwCommon.h"
+#include "cwLog.h"
+#include "cwCommonImpl.h"
+#include "cwMem.h"
+#include "cwObject.h"
+#include "cwB23Tree.h"
+
+cw::rc_t   cw::b23::test( const object_t* cfg )
+{
+  rc_t rc = kOkRC;
+
+  /*
+  typedef struct tree<unsigned,char*,kInvalidIdx> tree_t;
+
+  tree_t* t = create<unsigned,char*,kInvalidIdx>(4);
+
+  destroy(t);
+  */
+
+  typedef struct tree_str<unsigned,const char*,kInvalidIdx> tree_t;
+
+  tree_t t;
+  typedef struct kv_str
+  {
+    unsigned k;
+    const char* v;
+  } kv_t;
+
+  kv_t kvA[] = { {0,"zero"}, {1,"one"}, {2,"two"}, {3,"three"}, {4,"four"}, {5,"five"},
+                 {6,"siz"}, {7,"seven"}, {8,"eight"}, {9,"nine"},  {10,"ten"}, {11,"eleven"},
+                 {12,"twelve"}, {13,"thirt"}, {14,"fourt"}, {15,"fift"}, {16,"sixt"} };
+
+  unsigned kvN = sizeof(kvA)/sizeof(kvA[0]);
+  
+  t.create(4);
+
+  for(unsigned i=0; i<kvN; ++i)
+  {
+    t.insert(kvA[i].k,kvA[i].v);
+    t.print();
+  }
+
+  t.destroy();
+  
+  return rc;
+}
+
diff --git a/cwB23Tree.h b/cwB23Tree.h
new file mode 100644
index 0000000..b6d58f7
--- /dev/null
+++ b/cwB23Tree.h
@@ -0,0 +1,590 @@
+#ifndef cwB23Tree_h
+#define cwB23Tree_h
+
+namespace cw
+{
+  namespace b23
+  {
+
+    /*
+      This is a binary tree implemented as a (2-3 tree)
+      See: docs/2-3-trees.pdf
+      or https://cs.wellesley.edu/~cs231/handouts/2-3-trees.pdf
+     */
+      
+    
+    template< typename K, typename V, K null_key >
+    struct tree_str
+    {
+
+      typedef enum {
+        kInvalidNodeTId,
+        k1LeafTId,
+        k2LeafTId,
+        k2NodeTId,
+        k3NodeTId
+      } node_tid_t;
+      
+      typedef struct value_str
+      {
+        V value;
+        struct value_str* link;
+      } value_t;
+      
+      typedef struct key_value_str
+      {
+        K        key;     // Key for this k/v pair
+        value_t* valueL;  // Linked list of values which share the same key.
+        
+        bool is_empty() const { return key==null_key; }
+        bool is_not_empty() const  { return !is_empty(); }
+        void set_empty() { key=null_key; valueL=nullptr; }
+        
+      } key_value_t;
+
+
+      
+      typedef struct node_str
+      {
+
+        unsigned nid;
+        
+        struct node_str* parent;
+        struct node_str* l_link;
+        struct node_str* m_link;
+        struct node_str* h_link;
+
+        // If kv1 is not empty then kv1.key is > kv0.key
+        key_value_t kv0; // kv0 always contains a valid key-value pair
+        key_value_t kv1; // kv1 is only valid if this is a 3 node
+
+        unsigned key_value_count() const { return kv1.is_empty() ? 1 : 2; }
+
+        const K&  min_key() const { return kv0.key; }
+        const K&  max_key() const { return kv1.is_empty() ? kv0.key : kv1.key; }
+
+        // Leaf nodes have no child pointers, but may have one or two key-value pairs.
+        bool is_leaf() const   { return this->l_link == nullptr; }
+
+        bool is_1_leaf() const { return is_leaf() && kv1.is_empty(); }
+        bool is_2_leaf() const { return is_leaf() && kv1.is_not_empty(); }
+
+        // 2 nodes have one key-value pair and valid l_link and h_link;
+        bool is_2_node() const { return !this->is_leaf() && this->m_link == nullptr; }
+
+        // 3 nodes have two key-value pairs and valid l,m,h links
+        bool is_3_node() const { return !this->is_leaf() && this->m_link != nullptr; }
+
+        node_tid_t type_id() const { return is_leaf() ? (is_1_leaf() ? k1LeafTId : k2LeafTId) : (is_2_node() ? k2NodeTId : k3NodeTId); }
+
+        bool is_valid()
+        {
+          // if l_link is null then h_link and m_link are also null. if l_link is not null then neither is h_link.
+          bool fl0 = l_link==nullptr ? (h_link==nullptr && m_link==nullptr) : h_link!=nullptr;
+          
+          // kv0 is never empty
+          bool fl1 = kv0.is_not_empty() && kv0.valueL != nullptr;
+          
+          // m_link is null if kv1 is empty
+          bool fl2 = kv1.is_empty() ? m_link==nullptr : m_link!=nullptr;
+
+          return fl0 && fl1 && fl2;
+        }
+
+        
+      } node_t;
+
+      typedef struct node_block_str
+      {
+        struct node_block_str* link;
+        node_t*                nodeA;
+        unsigned               nodeN;
+        unsigned               next_avail_node_idx; // index next empty slot      
+      } node_block_t;
+
+      typedef struct value_block_str
+      {
+        struct value_block_str* link;
+        value_t*                valueA;
+        unsigned                valueN;
+        unsigned                next_avail_value_idx; // index of next empty slot
+      } value_block_t;
+
+      node_t*        _root = nullptr;
+      node_block_t*  _beg_node_block = nullptr;   // First node in node block linked list
+      node_block_t*  _end_node_block = nullptr;   // Last block in node block linked list (always partially empty)
+      value_block_t* _beg_value_block = nullptr;  // First node in value block linked list
+      value_block_t* _end_value_block = nullptr;  // Last block in value block linked list (always partially empty)
+      node_t*        _free_node_list = nullptr;   // Linked list, through 'parent' of avail nodes. 
+      unsigned       _nodes_per_block = 0;
+      unsigned       _values_per_block = 0;
+      unsigned       _nid = 0;
+
+      const char* node_tid_to_label( node_tid_t tid )
+      {
+        switch(tid)
+        {
+        case kInvalidNodeTId: return "<inv>";
+        case k1LeafTId: return "1L";
+        case k2LeafTId: return "2L";
+        case k2NodeTId: return "2N";          
+        case k3NodeTId: return "3N";
+        }
+        return "<unk>";
+      }
+
+      
+      // Return the node closest to the given key.
+      // 
+      node_t* key_to_node( K key )
+      {
+        node_t* n = _root;
+        while(n != nullptr)
+        {
+          if( n->kv0.key == key )
+            break;
+
+          if( n->kv1.is_not_empty() and n->kv1.key == key )
+            break;
+
+          if( key < n->kv0.key )
+          {
+            n = n->l_link;
+          }
+          else
+          {
+            if(  key > (n->kv1.is_not_empty() ? n->kv1.key : n->kv0.key) )
+              n = n->h_link;
+            else
+              n = n->m_link;
+          }
+        }
+
+        return n;
+      }
+      
+      node_block_t*  _alloc_node_block( unsigned nodes_per_block )
+      {
+        node_block_t* b = mem::allocZ<node_block_t>();
+        
+        b->nodeA   = mem::allocZ<node_t>( nodes_per_block );
+        b->nodeN   = nodes_per_block;
+
+        if( _beg_node_block == nullptr )
+          _beg_node_block = b;
+        else
+          _end_node_block->link = b;
+      
+        _end_node_block = b;
+
+        return b;
+      }
+
+      value_block_t*  _alloc_value_block( unsigned values_per_block )
+      {
+        value_block_t* b = mem::allocZ<value_block_t>();
+        
+        b->valueA   = mem::allocZ<value_t>( values_per_block );
+        b->valueN   = values_per_block;
+
+        if( _beg_value_block == nullptr )
+          _beg_value_block = b;
+        else
+          _end_value_block->link = b;
+      
+        _end_value_block = b;
+
+        return b;
+      }
+
+      void _alloc_value( key_value_t& kv, V new_value )
+      {
+        if( _end_value_block==nullptr || _end_value_block->next_avail_value_idx >= _end_value_block->valueN )
+          _alloc_value_block(_values_per_block);
+
+        assert( _end_value_block!= nullptr && _end_value_block->next_avail_value_idx < _end_value_block->valueN );
+
+        value_t* v = _end_value_block->valueA + _end_value_block->next_avail_value_idx++;
+
+        v->value = new_value;
+        v->link = kv.valueL;
+        kv.valueL = v;
+        
+      }
+
+      // Initialize a kv with a new key, value pair
+      void _init_key_value( key_value_t& kv, K key, V value )
+      {
+        kv.key = key;
+        _alloc_value(kv,value);
+      }
+
+      // Initialize a kv from an existing kv pair
+      void _move_key_value( key_value_t& lhs_kv, key_value_t& rhs_kv )
+      {
+        lhs_kv = rhs_kv;
+        rhs_kv.set_empty();
+      }
+
+      node_t* _alloc_node( node_t* parent )
+      {
+        node_t* n = nullptr;
+        
+        if( _free_node_list != nullptr )
+        {
+          n = _free_node_list;
+          memset(n,0,sizeof(*n));
+          _free_node_list = _free_node_list->parent;          
+        }
+        else
+        {
+          // if the current node block has no available nodes then create a new node block
+          if( _end_node_block==nullptr || _end_node_block->next_avail_node_idx >= _end_node_block->nodeN )
+            _alloc_node_block(_nodes_per_block);
+
+          // a node block with available nodes must now exist 
+          assert( _end_node_block!= nullptr && _end_node_block->next_avail_node_idx < _end_node_block->nodeN );
+          
+          // get the next available node
+          n = _end_node_block->nodeA + _end_node_block->next_avail_node_idx++;
+        }
+        
+        n->nid    = _nid++;
+        n->parent = parent;
+        n->kv0.key = null_key;
+        n->kv1.key = null_key;
+        return n;
+      }
+
+      // allocate a new node with a new key / value pair
+      node_t* _alloc_node( node_t* parent, K new_key, V new_value )
+      {
+        node_t* n = _alloc_node(parent);
+        
+        // all new nodes have a valid k/v pair in kv0
+        _init_key_value( n->kv0, new_key, new_value );
+        
+        return n;
+      }
+
+      // allocate a new node with an existing k/v apir.
+      node_t* _alloc_node( node_t* parent, key_value_t& kv )
+      {
+        node_t* n = _alloc_node(parent);
+        _move_key_value( n->kv0, kv );
+        return n;
+      }
+
+      void _free_node( node_t* node )
+      {
+        // track free nodes by forming a list using the 'parent' pointer
+        node->parent = _free_node_list;
+        _free_node_list = node;
+      }
+      
+      rc_t create( unsigned nodes_per_block )
+      {
+        rc_t rc  = kOkRC;
+
+        _nodes_per_block = nodes_per_block;
+        _values_per_block= nodes_per_block;
+
+        _alloc_node_block(nodes_per_block);
+        _alloc_value_block(nodes_per_block);
+        
+        return rc;
+      }      
+
+      void destroy()
+      {
+        value_block_t* vb = _beg_value_block;
+        while( vb!=nullptr )
+        {
+          value_block_t* vb0 = vb->link;
+          mem::release(vb->valueA);
+          mem::release(vb);
+          vb=vb0;
+        }
+
+        node_block_t* nb = _beg_node_block;
+        while( nb !=nullptr )
+        {
+          node_block_t* nb0 = nb->link;
+          mem::release(nb->nodeA);
+          mem::release(nb);
+          nb=nb0;
+        }
+      }
+
+      void _insert_into_1_leaf(node_t* n, K key, V value )
+      {
+        if( key > n->kv0.key )
+          _init_key_value(n->kv1,key,value);
+        else
+        {
+          _move_key_value(n->kv1,n->kv0);
+          _init_key_value(n->kv0,key,value);
+        }
+      }
+
+
+      node_t* _2_leaf_to_2_node_sub_tree( node_t* n, K key, V value )
+      {
+        assert( n->is_2_leaf() );
+        
+        if( key < n->kv0.key )
+        {
+          n->l_link = _alloc_node(n,key,value);
+          n->h_link = _alloc_node(n,n->kv1);            
+        }
+        else
+        {
+          if( key > n->kv1.key )
+          {
+            n->l_link = _alloc_node(n,n->kv0);
+            n->h_link = _alloc_node(n,key,value);
+            _move_key_value(n->kv0,n->kv1);
+          }
+          else
+          {
+            n->l_link = _alloc_node(n,n->kv0);
+            n->h_link = _alloc_node(n,n->kv1);
+            _init_key_value(n->kv0,key,value);
+          }
+        }
+
+        assert(n->is_2_node());
+        return n;
+      }
+
+      void _link_to_parent_l( node_t* parent, node_t* child )
+      {
+        parent->l_link = child;
+        child->parent = parent;
+      }
+      
+      void _link_to_parent_m( node_t* parent, node_t* child )
+      {
+        parent->m_link = child;
+        child->parent = parent;
+      }
+      void _link_to_parent_h( node_t* parent, node_t* child )
+      {
+        parent->h_link = child;
+        child->parent = parent;
+      }
+
+      
+      // convert 'n', a 2-node, into a 3-node by absorbing it's 2-node child 
+      void _2_node_to_3_node( node_t* n, node_t* child )
+      {
+        assert( n->is_2_node() );
+        
+        // if child is the l subtree
+        if( child == n->l_link )
+        {
+          _move_key_value(n->kv1,n->kv0);
+          _move_key_value(n->kv0,child->kv0);
+
+          _link_to_parent_l(n,child->l_link);
+          _link_to_parent_m(n,child->h_link);
+          
+        }
+        else  // child must be the h subtree
+        {
+          assert( child == n->h_link );
+
+          _move_key_value(n->kv1,child->kv0);
+
+          _link_to_parent_m(n,child->l_link);
+          _link_to_parent_h(n,child->h_link);
+        }
+
+        _free_node(child);
+
+        assert( n->is_3_node() );
+      }
+
+      node_t* _2node_from_parts( node_t* parent, key_value_t& kv, node_t* l_subtree, node_t* h_subtree )
+      {
+          node_t* h_node = _alloc_node(parent,kv);
+          _link_to_parent_l(h_node,l_subtree);
+          _link_to_parent_h(h_node,h_subtree);
+          return h_node;
+      }
+
+      // Convert a 3-node to a balanced 2-node.
+      // 'child' is a balanced sub-trees of 'n' 
+      void _3_node_to_balanced_2_node( node_t* n, node_t* child )
+      {
+        assert( n->is_3_node() );
+        assert( child->is_2_node() );
+
+        // if the child is on the l-subtree
+        if( child == n->l_link )
+        {
+          // make l-key the central node and the h-key the balanced h-subtree
+          n->h_link = _2node_from_parts(n,n->kv1,n->m_link,n->h_link);
+        }
+        else
+        {
+          if( child == n->h_link )
+          {
+            // make h-key the central node and l-key the balanced l-subtree
+            n->l_link = _2node_from_parts(n,n->kv0,n->l_link,n->m_link);
+            _move_key_value(n->kv0,n->kv1);            
+          }
+          else
+          {
+            // make m-subtree he central node and l-key the balanced l-subtree and h-key the balanced h-subtree
+            assert( child == n->m_link );
+            n->l_link = _2node_from_parts(n,n->kv0,n->l_link,child->l_link);
+            n->h_link = _2node_from_parts(n,n->kv1,child->h_link,n->h_link);
+            _move_key_value(n->kv0,child->kv0);
+          }
+        }
+
+        // n is now a 2-node - remove the old m_link
+        n->m_link = nullptr;
+        
+        assert( n->is_2_node() );
+        assert( n->l_link->is_2_node() );
+        assert( n->h_link->is_2_node() );
+      }
+      
+      void _insert_up( node_t* n, node_t* sub_tree )
+      {
+        while(1)
+        {
+            // if n is null then the root was already processed and we are done
+          if( n == nullptr )
+            break;
+          
+          if( n->is_2_node() )
+          {
+            // if n is a 2-node the sub-tree is absorved ...
+            _2_node_to_3_node(n,sub_tree); 
+            break; // .. and we are done
+          }
+          else // n is a 3-node
+          {
+            // only 2-nodes and 3-nodes can be accessed when going up the tree
+            assert( n->is_3_node() );
+            
+            // create a balanced 2-node from the 3-node + sub-tree
+            _3_node_to_balanced_2_node(n,sub_tree);
+
+            // the tree may now be imbalanced to continue upward
+            sub_tree = n;
+            n = n->parent;
+          }
+        }
+      }
+      
+      void _insert_down( node_t* n, K key, V value )
+      {
+        while(1)
+        {
+          if( key == n->kv0.key )
+          {
+            _alloc_value(n->kv0,value);
+            return;
+          }
+
+          if( n->kv1.is_not_empty() && key == n->kv1.key )
+          { 
+            _alloc_value(n->kv1,value);
+            return;
+          }
+          
+          switch( n->type_id() )
+          {
+          case k1LeafTId:
+            _insert_into_1_leaf(n,key,value);
+            return; // the new k/v was absorbed - we're done.
+            
+          case k2LeafTId:
+            if( key == 10 )
+            {
+              printf("break");
+            }
+            _insert_up( n->parent, _2_leaf_to_2_node_sub_tree(n, key, value ));
+            return; // the new k/v inserted on the upward path
+            
+          case k2NodeTId:
+            n = key < n->kv0.key ? n->l_link : n->h_link;
+            break;
+            
+          case k3NodeTId:
+            n = key < n->kv0.key ? n->l_link : (key < n->kv1.key ? n->m_link : n->h_link);
+            break;
+            
+          default:
+            assert(0);
+          }
+          
+        }
+      }
+      
+      void insert( K key, V value )
+      {
+        if( _root == nullptr )
+          _root = _alloc_node(nullptr,key,value);
+        else
+          _insert_down(_root,key,value);        
+      }
+
+      void delete( K key )
+      {
+        // if key is found on internal node - replace with in-order successor.
+        // if in-order successor is on a non-leaf node continue replacing
+        // with in-order successor until the replacement leaves a hole
+        // in a leaf node.
+        // If the terminal node with the hole is a 2-leaf then change it to a 1-leaf : DONE
+        // if the terminal node is a 3-leaf then
+      }
+
+      
+
+      
+      void _print( const node_t* n, unsigned level )
+      {
+        if( n->l_link != nullptr )
+          _print(n->l_link,level + 1);
+
+        unsigned pnid = n->parent==nullptr ? 666 : n->parent->nid;
+        printf("%i k0:%i %s id:%i par:%i\n",level,n->kv0.key,node_tid_to_label(n->type_id()),n->nid,pnid);
+        
+        if( n->m_link != nullptr )
+          _print(n->m_link,level+1);
+        
+        if( n->kv1.is_not_empty() )
+          printf("%i k1:%i %s id:%i par:%i\n",level,n->kv1.key,node_tid_to_label(n->type_id()),n->nid,pnid);
+            
+        if( n->h_link != nullptr )
+          _print(n->h_link,level+1);
+          
+                
+      }
+      
+      void print(const node_t* n = nullptr)
+      {
+        unsigned level = 0;
+        
+        if( n == nullptr )
+          n = _root;
+        _print(n,level);
+        printf("done\n");
+        
+      }
+      
+    };
+
+    rc_t test( const object_t* cfg );
+  }
+
+}
+
+
+    
+#endif