ISO 9660 Standard - File System for CD-ROM

The main characteristics of ISO 9660 standard are:
1. Reserved Field - The first 16 sectors of the track is reserved. The reserved field can be used to store computer code to boot the operating system. This makes the CD bootable. But most of the time, the reserved field is empty, containing zeros.
2. Volume Descriptors - Several consecutive sectors, starting from sector 17, are used as volume descriptors. A volume descriptor uses one sector on the track, and stores description of the contents and kind of information contained on the track.
3. Primary Volume Descriptor - A volume descriptor with the first byte (volume descriptor type indicator) set to 1. An ISO 9660 file system requires at least one primary volume descriptor. The primary volume descriptor contains the volume identifier, creation date, location of root directory block, and other information.
4. Root Directory Block - Several consecutive sectors, located after volume descriptors, is used to store directory records of the root directory. A directory record stores the location of file block, or a sub directory block, and other related information.
5. File Name - ISO 9660 allows a file name to have an extension. But it permits only capital letters, digits and underscores in file names and extensions.
6. Directory Name - ISO 9660 does not allow a directory to have an extension. It permits only capital letters, digits and underscores in directory names.