CD-R media are less expensive and more convenient than portable hard disks, removable hard disk media and floppy disks. Almost every computer built in the last three years is equipped with a CD-ROM drive. ISO-9660 format file names also optionally support version numbers. The most common of these is a hybrid Macintosh HFS, ISO-9660 format. Files may be shared between the partitions without duplication to save space.
Audio CDs have another format.
In general, CD-R media may only be written once. Multisession disks are possible, but they are more likely to result in errors and compatibility problems. The methods for preparation of the data depend on the data to be stored. Files for backup are prepared with backup software such as Dantz Retrospect. Backup software can select only those files created or modified since the last backup and can compress the files to save space.