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CDs are round and shiny, and although they all look the same, they come in several flovours, and several formats. The following chapters discuss the physical formats which have evolved over time and with enhanced drive capabilities. Relevant key terms are

• Disk at once (DAO)
• Track at once (TAO)
• Session at once
• Packet writing

The formats have evolved generally to allow smaller sections of the disk to be written at a time.  This means that for multiple session disks, there is less wasted overhead when a session is added. The logical capacity of a disk can also vary.  All this detail information can sometimes assist with a forensic investigation, so the CnW Recovery program will whenever possible determine, and log the details of the disk.

Other critcial points to understand about disk is if a disk is open or closed.  Other terms that will be discussed are Run in, Run out and TOC (table of contents). These are all parts of the physical recording of a disk that are normally only seen by the CD reader, and not the application reading the logical disk.

When it comes to RW disks, there are other variations possible.

Any modern CD-RW or DVD-RW will read all variations of disks, but there can be limitations.

Although logically similar many of the CD concepts are not part of DVDs.