.CTO file extension

This is the basic program to work with .CTO extension

ChessBase Light 2007 ChessBase openings book

.CTO extension is also supported by the following programs:

ChessBase 9 ChessBase openings book

ChessBase ChessBase openings book

ChessBase 13 is a personal, stand-alone chess database.

ChessBase Reader ChessBase openings book

Open chess games database files and play through the games.