: Once extracted from the .rar archive, the data is typically in formats like .ctg , .hbg , or .hcs , which are compatible with various chess graphical user interfaces (GUIs) like HIARCS Chess Explorer or Fritz. How to Use It

: Use a tool like WinRAR , 7-Zip , or The Unarchiver to unpack the .rar file.

: In your chess software (e.g., ChessBase ), look for "Opening Book" or "Live Book" settings to select the extracted file. HIARCS Chess Opening Books

: Using a dedicated tournament book can improve an engine's strength significantly—sometimes by as much as 40 Elo points .