Update Description.txt

VBA7_64BitOperations/Description.txt

@@ -1,6 +1,34 @@
-List of functions in module 'bas64BitOperations'	
-
 Emulate ULongLong 64 bit unsigned integer operations	
+====================================================
+
+The problem with VBA/VB6 is that there are no 64-bit unsigned integers (ULongLong) available.
+
+The module 'bas64BitOperations.bas' contains functions to emulate bit operations for 64-bit unsigned integers.
+
+For 32-bit MsOffice VBA or VB6 we can use two Long 32-bit signed integers combined in a new datatype TBit64.
+
+    this requires functions for basic bit operations like AND, OR, XOR, NOT.
+
+For 64-bit MsOffice VBA7 we can use the new 64-bit signed integer datatype LongLong.
+
+    basic bit operations like AND, OR, XOR, NOT do NOT need extra functions but can be used directly.
+
+Functions available for both variants are:
+
+    SetBit64, ClearBit64, ShiftLeft64, ShiftRight64, PopCnt64 (number of bits set),
+
+    Lsb64 (position of left most bit), Rsb64 (position of left most bit) and some more.
+
+The Ms-Excel file VBA7.xlsm shows how to use these functions for 32/64-bit MsOffice.
+
+For 64-bit Excel there is also a simple chess demonstration how to use 64-bit chessboard logic.
+
+(for the best Excel/VB6 chess program available please see my project at github.com/RZulu54/ChessBrainVB)
+
+----------------------------------------------------------------------------------------------
+
+List of functions in module 'bas64BitOperations'	
+================================================
 
 call Init32Bit before	call Init64Bit before	
 32-bit mode		64-bit mode	Some logic needed to handle the sign bit