diff --git a/source/Debugger/Debugger_DisassemblerData.cpp b/source/Debugger/Debugger_DisassemblerData.cpp
index de5dda07..b4ad843a 100644
--- a/source/Debugger/Debugger_DisassemblerData.cpp
+++ b/source/Debugger/Debugger_DisassemblerData.cpp
@@ -63,7 +63,7 @@ void _GetAutoSymbolName ( const Nopcode_e &nopcode, const WORD nStartAddress, ch
 
 // @param tData_ Filled out with range data
 //===========================================================================
-WORD _CmdDefineByteRange(int nArgs,int iArg,DisasmData_t & tData_)
+WORD _GetDataRange (int nArgs, int iArg, DisasmData_t& tData_)
 {
 	WORD nAddress  = 0;
 	WORD nAddress2 = 0;
@@ -76,12 +76,14 @@ WORD _CmdDefineByteRange(int nArgs,int iArg,DisasmData_t & tData_)
 	// DB symbol
 	// bool bisAddress ...
 
-	if( nArgs < 1 )
+	if (nArgs < 1)
 	{
 		nAddress = g_nDisasmCurAddress;
 	}
 	else
 	{
+		// DB foo = 300 // nArgs == 3
+
 		RangeType_t eRange = Range_Get( nAddress, nAddress2, iArg);
 		if ((eRange == RANGE_HAS_END) ||
 			(eRange == RANGE_HAS_LEN))
@@ -108,10 +110,23 @@ WORD _CmdDefineByteRange(int nArgs,int iArg,DisasmData_t & tData_)
 
 	tData_.nStartAddress = nAddress;
 	tData_.nEndAddress = nAddress + nLen;
-//	tData_.nArraySize = 0;
+
+	return nAddress;
+}
+
+//===========================================================================
+WORD _CmdDefineByteRange(int nArgs,int iArg,DisasmData_t & tData_)
+{
+	WORD nAddress  = 0;
+	WORD nAddress2 = 0;
+	WORD nEnd      = 0;
+	int  nLen      = 0;
+
+	nAddress = _GetDataRange(nArgs,iArg,tData_);
 
 	const char *pSymbolName = "";
 	char aSymbolName[ MAX_SYMBOLS_LEN+1 ];
+
 	SymbolTable_Index_e eSymbolTable = SYMBOLS_ASSEMBLY;
 	bool bAutoDefineName = false; // 2.7.0.34
 
@@ -138,20 +153,27 @@ WORD _CmdDefineByteRange(int nArgs,int iArg,DisasmData_t & tData_)
 	//   DB 801
 	if( bAutoDefineName )
 	{
-		if( g_iCommand == CMD_DEFINE_DATA_STR )
-			sprintf( aSymbolName, "T_%04X", tData_.nStartAddress ); // ASC range
-		else
-		if( g_iCommand == CMD_DEFINE_DATA_WORD1 )
-			sprintf( aSymbolName, "W_%04X", tData_.nStartAddress ); // DW range
-		else
-			sprintf( aSymbolName, "B_%04X", tData_.nStartAddress ); // DB range
+		Nopcode_e nopcode = NOP_BYTE_1;
 
+		bool isString = (g_iCommand == CMD_DEFINE_DATA_STR);
+		if( isString )
+			nopcode = NOP_STRING_ASCII;
+
+		bool isWord1 = (g_iCommand == CMD_DEFINE_DATA_WORD1);
+		if( isWord1 )
+			nopcode = NOP_WORD_1;
+
+		bool isAddr = (g_iCommand == CMD_DEFINE_ADDR_WORD);
+		if( isAddr )
+			nopcode = NOP_ADDRESS;
+
+		_GetAutoSymbolName( nopcode, tData_.nStartAddress , aSymbolName );
 		pSymbolName = aSymbolName;
 	}
 
 	// bRemoveSymbol = false // use arg[2]
 	// bUpdateSymbol = true // add the symbol to the table
-	SymbolUpdate( eSymbolTable, pSymbolName, nAddress, false, true ); 
+	SymbolUpdate( eSymbolTable, pSymbolName, nAddress, false, true );
 
 	// TODO: Note: need to call ConsoleUpdate(), as may print symbol has been updated
 
@@ -161,18 +183,38 @@ WORD _CmdDefineByteRange(int nArgs,int iArg,DisasmData_t & tData_)
 }
 
 // Undefine Data
+//
+//     X
+//     X addr
+//     X addr:addr
+//
+// Example:
+//     DB hgr 2000:3FFF
+//     U 1FFF
+//     X 1FFF:2001
 //===========================================================================
 Update_t CmdDisasmDataDefCode (int nArgs)
 {
 	// treat memory (bytes) as code
-	if (! ((nArgs <= 2) || (nArgs == 4)))
+	if (! ((nArgs <= 2) || (nArgs == 4)) && (nArgs != 3))
 	{
 		return Help_Arg_1( CMD_DISASM_CODE );
 	}
 
-	DisasmData_t tData;
-	int iArg = 2;
-	WORD nAddress = _CmdDefineByteRange( nArgs, iArg, tData );
+	DisasmData_t tData; // X 1FFF:2001
+	WORD nAddress  = 0; // 8191
+	int  iArg      = 0;
+
+	if (nArgs == 3)
+	{
+		iArg = 1; // #### : ####
+		nAddress  = _GetDataRange( nArgs, iArg, tData );
+	}
+	else
+	{
+		iArg      = 2;
+		nAddress  = _GetDataRange( nArgs, iArg, tData );
+	}
 
 	// Need to iterate through all blocks
 	// DB TEST1 300:320
@@ -180,18 +222,72 @@ Update_t CmdDisasmDataDefCode (int nArgs)
 	// DB TEST3 320:340
 	// X  TEST1
 
-	DisasmData_t *pData = Disassembly_IsDataAddress( nAddress );
-	if( pData )
-	{
-		// TODO: Do we need to split the data !?
-		//Disassembly_DelData( tData );
-		pData->iDirective = _NOP_REMOVED;
+	/*
+        // Edge cases:
+        U 1FFF
+        DB 2000:2005
+        X 1FFF:2001 // Chop 2 head
+        X 2004:2006 // Chop 2 tail
+        X 1FFF:2006 // Chop entire
 
-		// TODO: Remove symbol 'D_FA62' from symbol table!
-	}
-	else
+        U 1FFF
+        DB 2000:2000
+        X  2000:2000 // Chop entire
+
+        U 1FFF
+        DB 2000:2002
+        X  2001:2001 // Chop middle
+
+        U 1FFF
+        DB 2000:2005
+        X  2002:2003 // Chop middle
+	*/
+	while (nAddress <= tData.nEndAddress)
 	{
-		Disassembly_DelData( tData );
+		DisasmData_t *pData = Disassembly_IsDataAddress( nAddress );
+		if( pData )
+		{
+			if ((      nAddress    <= pData->nStartAddress)
+			&&  (tData.nEndAddress >= pData->nEndAddress  ))
+			{
+				// remove entire
+				Disassembly_DelData( *pData );
+			}
+			else
+			if ((      nAddress      <= pData->nStartAddress)
+			&&  (tData.nStartAddress <  pData->nEndAddress  ))
+			{
+				// head
+				pData->nStartAddress = nAddress+1;
+			}
+			else
+			if ((      nAddress    >  pData->nStartAddress)
+			&&  (tData.nEndAddress >= pData->nEndAddress  ))
+			{
+				// tail
+				pData->nEndAddress = nAddress-1;
+			}
+			else
+			{
+				// middle
+				SymbolTable_Index_e eSymbolTable = SYMBOLS_ASSEMBLY;
+
+				DisasmData_t tSplit = *pData;
+				pData->nEndAddress = nAddress - 1;
+
+				const char *pSymbolName = tSplit.sSymbol;
+
+				tSplit.nStartAddress = tData.nEndAddress + 1; // nAddress + 1;
+				_GetAutoSymbolName( pData->eElementType, tSplit.nStartAddress, tSplit.sSymbol );
+
+				SymbolUpdate( eSymbolTable, pSymbolName, tSplit.nStartAddress, false, true );
+				Disassembly_AddData( tSplit );
+			}
+
+			// TODO: Remove symbol 'D_FA62' from symbol table!
+		}
+
+		nAddress++;
 	}
 
 	return UPDATE_DISASM | ConsoleUpdate();