A 6-byte area in the ID area has been established for free use by applications. Stored in this area is information unique to each application, such as file system information and comments. The ID, however, is in the ROM area, so its value cannot be changed during game execution. In the free area, each company can freely assign values. Consequently, the company code must first be checked when data recorded in the free area are used during a game. In such cases, data such as the initial code must also be checked as necessary.

With most games, performing a comparison between the entire ID area does not cause problems such as destruction of data in other disks. However, with games that assume the use of multiple disks during the game, discrete data such as initial codes and company names/free areas must be compared to prevent accidental data destruction.