Reference on D88 disk image format
To investigate what code gets executed when a disk is loaded in one of the Japanese computers, we can investigate the contents of the disk image. Disk images for many Japanese computers are often distributed in the D88 format. Luckily it is a simple format and there's a reference about it in English here: https://www.z88dk.org/tools/x1/XBrowser_User_Guide.pdf Look in Appendix II. It is a reference to a tool intended for Sharp X1 users, but the format is the same used in PC88 and other Japanese computer emulators and tools. The information is organized by tracks and then by sectors, as in a real disk. File header The file begins with a header with the following fields: struct header { char[17] name; // image name, usually empty u8[9] reserved; // reserved, usually zero u8 write_protect; // non-zero value means write-protected disk u8 media_type; // 0: 2D, 0x10: 2DD, 0x20: 2HD, 0x30: 1D, 0x40: 1DD u32 disk_size; //