.CTO file extension

This is the basic program to work with .CTO extension

ChessBase Light 2007 ChessBase openings book

The program works with the following extensions: cbz, cib, cit, ck1, cbs, ck2, cko, ck3, cba, ckn, cbb, cp1, cbc, cp2, cbe, cp3, cbf, cpn, cpo, ctb, cbh, ctg, cbm, cto, cbp, pgi, cbt, pgn, cbv and cbgi

.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.