The entire CD technology family conforms to a set of international standards, commonly referred to as color books, to ensure all CDs are compatible with other CD players -ROM drives. Even though the basic construction of every CD is the same, their formats vary by use.

RED BOOK defines a CD Audio standard for the common audio CDs you buy with commercial music or voice from a retail outlet.
Unlike your home CD burning (where a laser alters a dye layer on a CD-R), CD mass manufactured discs for sale are physically stamped to get pits and lands on the Compact Disc.

The Glass Master: A high-powered laser etches the digital data onto a photosensitive glass master disc.
Stamper: This master is used to create a metal stamper (a negative mold of the pits and lands).
Injection Molding: Polycarbonate plastic is injected into a mold containing the metal stamper, physically imprinting the data track into the disc.
Metallization: A micro-thin layer of aluminum is applied to reflect the laser, followed by a protective lacquer and the printed commercial label.

Red Book Standard Requirements:
Audio Format: Strictly 2-channel (stereo) 16-bit/44.1kHz uncompressed digital audio.
Track Capacity: A maximum of 99 audio tracks.
Error Correction: Uses Cross Interleave Reed-Solomon Code (CIRC) for heavy error protection.
Table of Contents: Contains a mandatory lead-in area with a Table of Contents (TOC) pointing to track locations.

YELLOW BOOK defines a CD-ROM standard that specifies how data is arranged on a CD-ROM. The Yellow Book has sub-books that define CD-XA discs. 

GREEN BOOK defines a Compact Disc Interactive (CD-I) standard for a special multimedia format that can be played on a set-top player attached to a television set. 

WHITE BOOK defines a Video CD standard for MPEG-1 video discs played on a set-top player attached to a television set. You can buy full length Video CD movies, however, the quality isn't quite as good as DVD. 

BLUE BOOK defines a CD Extra standard that specifies a way to put both CD audio tracks and computer data on the same disc, but in different sessions, or recording areas. The audio session is recorded first, then the data session. This way, when the disc is played in a CD player, only the audio tracks can be seen and played. When the same disc is placed in a standard multi-session CD-ROM drive, the audio tracks and the data track will be visible. 

ORANGE BOOK defines a CD-R -RW standard that specifies how the above formats are stored on CD-R -RW discs that you can record. The Orange Book is broken down into 3 parts, one for CD-MO, one for CD-R (called Orange Book part II), and one for CD-RW (called Orange Book part III). 

Red Book - CD Audio

The Red Book describes the physical properties of the compact disc and the digital audio encoding. It comprises:

• Audio specification for 16-bit PCM.
• Disc specification, including physical parameters.
• Optical stylus and parameters.
• Deviations and block error rate.
• Modulation system and error correction.
• Control and display system (ie subcode channels) & CD Graphics

The current status and versions of the Red Book and extensions are listed below.

The Red Book is also available as the international standard, ISO/IEC 60908, and is available in English and French from the International Electrotechnical Commission (IEC), http://www.iec.ch/.

Yellow Book - CD-ROM & CD-ROM XA

The Yellow Book comprises the CD-ROM specification plus an extension for CD-ROM XA. The Yellow Book for CD-ROM was written in 1984 to describe the extension of CD to store computer data. This specification comprises the following:

• Disc specification, optical stylus parameters, modulation and error correction and control & display system (from Red Book)
• Digital data structure, which describes the sector structure and the ECC and EDC for a CD-ROM disc.

• Disc format including Q channel and sector structure using Mode 2 sectors.
• Data retrieval structure based on ISO 9660 including file interleaving which is not available for Mode 1 data.
• Audio and graphics encoding (now obsolete)

The current status and versions of the Yellow Book and associated CD-ROM XA specification are listed below.

The Yellow Book is also available as the international standard, ISO/IEC 10149, and is available in English from the International Electrotechnical Commission (IEC), http://www.iec.ch/.

White Book - Video CD

The White Book defines the Video CD specification and comprises:

• Disc format including use of tracks, Video CD information area, segment play item area, audio/video tracks and CD-DA tracks.
• Data Retrieval Structure, compatible with ISO 9660.
• MPEG audio/video track encoding.
• Segment play item encoding for video sequences, video stills and CD-DA tracks.
• Play sequence descriptors for pre-programmed sequences.
• User data fields for scan data (enabling fast forward/reverse) and closed captions.
• Examples of play sequences and playback control.

The various Video CD formats and enhancements are listed in the table below.

Blue Book - Enhanced CD

The Blue Book defines the Enhanced Music CD (also known as CD Extra) specification for multisession pressed disc (ie not recordable) comprising audio and data sessions. These discs are intended to be played on any CD audio player, on PCs and on future custom designed players. The Blue Book comprises:

• Disc specification and data format including the two sessions (audio and data).
• Directory structure (to ISO 9660) including the directories for CD Extra information, pictures and data. It also defines the format of the CD Plus information files, picture file formats and other codes and file formats.
• MPEG still picture data format.

Last updated: Version 1.0, Dec 1995

Photo CD Book

Photo CD has been specified by Kodak and Philips based on the CD-i Bridge specification. It comprises the following:

• General Disc format including example of program area layout, index table, volume descriptor, data area, subcode Q-channel skew, CD-DA clips and microcontroller readable sectors.
• Data retrieval structures including directory structure, the INFO.PCD file and microcontroller readable sectors system
• Image data coding including a description of image coding and image packs.
• ADPCM files for simultaneous playback of audio and images by interleaving
• Playback program system including playlist files.

Last updated: Dec 1994

Multisession CD

Multisession CD specification for pressed discs is a Philips/Sony standard (actually yellow in colour) defining discs which have two or more sessions but are pressed not recordable.

The only pressed multisession disc format currently defined is the Enhanced Music CD, defined in the Blue Book.

The latest version of the Multisession CD book (Version 1.0, December 1995) defines the following:

• Data Format (including Sector Layout, Table of Contents, Program Area of each session and Lead-Out Area of each session)
• Data Retrieval Structure ie the ISO 9660 file system.

Last updated: Dec 1995

Orange Book - CD-R and CD-RW

The Orange Book defines CD-Recordable discs with multisession capability.

All three parts contain the following sections:

• Disc specification for unrecorded and recorded discs.
• Pre-groove modulation .
• Data organization including linking.
• Multisession and hybrid discs
• Recommendations for measurement of reflectivity, power control etc

These books define the characteristics of the recorder and blank discs, and how to perform the recording. One of the unique features of a CD-ROM is its ISO9660 file system, sometimes called the logical format. ISO9660 defines the format in which files and folders are arranged on a CD-ROM so a computer can locate them. The system is cross-platform compatible, so that standard CD-ROMs can be read by PCs, Macintosh and even UNIX systems. Of course, application programs are designed for specific types of computer platforms, but the actual files and folders are visible under other platforms. Hybrid CD-ROM discs combine ISO9660 with another native file system, such as the Macintosh or UNIX operating systems. These discs contain native PC and native Macintosh (or UNIX) sections, and display only the files for the type of computer reading the disc. 

Today, CD-ROM discs are used to distribute software and information on a large scale. Since most PCs today have CD-ROM drives built in, distributing application programs and data is a snap. In the past, an application program that took 20 floppy disks to install can easily be placed on a single CD-ROM disc. The user simply starts the installation process and can walk away-no more swapping floppy disks! Because CD-ROM discs are inexpensive to produce, hold up to 650 MB of data and have wide compatibility with popular computer systems, they are ideal for distributing large amounts of data or applications to computer users. 

CD Recordable (CD-R) Technology Compact Disc Recordable technology was developed in the early 1990s as a tool for software developers who wanted to prototype discs before stamping thousands of them. The first CD recorders cost over $100,000 and were as big as washing machines. The blank discs cost more than $100. Today, an entry-level CD-R drive costs under $300, looks just like a CD-ROM drive and the blank CD-R discs cost only a few dollars. CD-R discs can hold up to 650MB of computer data, or up to 74 minutes of quality CD music. CD-R is a "write once" technology-once the data is recorded, it is permanent and cannot be changed or erased. The data from the computer is broken down into "1s" and "0s" and burned into the recording layer of the CD-R disc as dark spots. Data is read back from a CD-R disc just like a regular CD-ROM. However, CD-R discs look different than regular CDs. They are usually gold on the label side, while the other side might be green or gold, depending on the recording material. Once CD-R discs are recorded, they can be read by any standard CD-ROM drive or CD player, because the recorded disc "looks" the same as a stamped CD to the player. Data can be added to CD-R discs in "sessions", but not erased. CD-R Compatibility The ISO9660 file system is typically used to record a CD-ROM, in order to ensure compatibility with multiple CD-ROM drives and operating systems. However, a newer file system called Universal Disc Format (UDF), a more flexible and efficient format for recording CDs, is also becoming popular. ISO9660 was designed for read-only discs and is cross compatible, but not ideal for writing files and folders one at a time. Of course, the other popular format is CD audio, which is universal for playing audio discs in any CD player, CD-ROM or even DVD-ROM drive. 

CD-ReWritable (CD-RW) Technology Compact Disc ReWritable technology is a recent addition to the CD family and a natural extension of CD-Recordable technology. As its name suggests, a CD-RW disc can be erased and re-written, in the same way a floppy disk can be erased or re-formatted. Just like CD-R discs, CD-RW discs hold up to 650 MB of data or 74 minutes of CD quality music. CD-RW discs are silver on the label side, just like a stamped CD, however, the recording side is a dark gray color. CD-RW uses a technology called "phase change" to record a "mark" on the disc that simulates a pit. This is accomplished by heating the spot to be recorded to a specific temperature very quickly. The mark can be changed by heating the spot again to a lower temperature, causing it to re-crystallize. This cycle can happen about 1,000 times on current CD-RW media. CD-RW Compatibility While CD-RW discs can be erased and re-written, they cannot be read by all standard CD-ROM drives and CD players. The phase change recording material of a CD-RW disc isn't as reflective as a stamped disc or even a CD-R disc. As a result, the recorded CD-RW discs are only readable in CD-ROM drives that advertise CD-RW compatibility, or that conform to the new Multi-Read specification.

While most new CD-ROM drives sold today are compatible with CD-RW discs, there are many drives already installed in computers that cannot read these discs. However, CD-RW discs were not designed to replace CD-R, in fact they are complementary technologies. A CD-ReWritable recorder is a multi-function drive. It can record a CD-RW or a CD-R disc. Since CD-RW discs cost more than CD-R discs, and are not as compatible with CD-ROM drives installed in the field, CD-R discs remain the best medium for distributing large files and data. CD-RW, because it is rewritable, is better for general data storage (personal file storage) or daily back ups, whenever data is frequently updated. CD-RW is also an ideal prototyping medium for making a CD-ROM that will eventually be stamped. If a problem is found in the program, a change can be made and the CD-RW disc re-burned with the new information. When the project is done, a CD-R disc can be recorded as a master. CD-R -RW work together to meet all your information management needs. 

CD-RW Recording Software The same CD recording software used to record a CD-R disc can be used to record a CD-RW disc. All the same disc formats apply to CD-RW. You can record music onto a CD-RW disc, however, you probably wouldn't be able to play it in your car or home stereo. For that application, use a CD-R disc in the recorder. Pre-mastering software that supports CD-RW discs usually has an option to erase or "blank" a CD-RW disc. This is necessary, as a CD-RW disc recorded with this type of software looks like a regular CD-ROM or CD Audio disc to the CD recorder once it has been written. Drive Letter Access software can directly overwrite a file with CD-RW media so you should never have to erase this kind of disc. 

Q: Can I make my own music CDs with a CD-RW drive? 
A: Yes, creation of music CDs that will play in standard CD players are supported . Sony CD-RW kits come with software that even helps you create your own music! 

Q: How much information can a CD hold? 
A: A 12cm CD can contain up to 650MB of computer data, or up to 74 minutes of stereo music. 

Q: What is the difference between CD-R and CD-RW discs? 
A: CD-Recordable (CD-R) discs record information permanently. You can add information to a disc until it is full, but not erase. The benefit however, is that CD-R discs are compatible with all CD players and CD-ROM drives.

  CD-ReWritable (CD-RW) discs hold the same amount of information as a CD-R disc, but are fully erasable and rewritable. Not all CD-ROM drives, and few CD players, can read a CD-RW disc. 

Q: How long does it take to record a CD? 
A: Depending how fast your CD recorder "burns", it can take as little as 5 minutes to record a full 650MB disc (12X), or as long as 74 minutes (1X). 

Q: Do I need any special training to use a CD recorder? 
A: If you can use a mouse, you can use CD recorder. With a few mouse clicks you can be recording CDs within minutes of installing your drive. 

Q: Can I erase and re-use music CDs that I've purchased in the past? 
A: No, CD recorders can only record on CD-R and CD-RW discs. Other CDs can be read or played in a CD recorder, but not recorded. 

Q: What can I do with a CD recorder? 
A: Common applications include: Creation of custom music CDs, system back ups, large file sharing, creation of video CDs to share, creation of digital photo albums, etc. There is virtually no limit to what you can do! 

Q: How long will a CD-R or CD-RW disc be usable? 
A: Both CD-R and CD-RW discs have an expected life greater than 30 years.