MIL-HDBK-9660B
2. Directory names are limited to eight characters with no extension.
3. Hierarchical file structure is limited to eight levels. It cannot support symbolic links.
4. Special file types that Unix applications require to run cannot be translated into ISO
9660.
5. ISO 9660 was specified for Read Only. It does not support incremental write and other CD-R features.
6. Original CDs allowed only one session - the beginning and end of a session were marked by a set of lead-in and lead-out blocks. CD-ROM players built before about
1991 were not designed to read past the lead out.
7. The volume descriptor, which contains information about the contents of the disc, is located at sector 16 of the first track. The location of all files and directories on the disc must be included in the path and directory tables in sector 16 in order to be accessible. This makes it impossible to append information to a writable disc recorded in ISO 9660.
8. ISO 9660 is inadequate for CD-RW (rewritable) and DVD (Digital Video/Versatile
Disc) discs.
A.5. CD-R (COMPACT DISC-RECORDABLE)
A.5.1 General. CD-R's widespread popularity deserves additional discussion. CD-Rs are used as backup storage for local and/or network hard drives, large graphic files and/or video clips, or to create full blown multimedia productions. Virtually anyone with a CD recorder and some software can create compact discs at their desktop. Most recorders can write CDs conforming to any of the "colored books."
A.5.2. CD-R Format and Physical Layout. A CD-R disc is physically identical to the Red Book, its capacity is listed in terms of time. Logically (file structure), a CD-R conforms to ISO 9660, but there are some differences between a CD-R and a prerecorded CD-ROM. Both have a polycarbonate substrate layer and a protective lacquer coating. However, a conventional CD-ROM's pits and lands (indicating information) are stamped onto an aluminum layer and covered with a plastic coating during the injection molding process of factory replication. A blank CD-R is prestamped with a single continuous spiral groove but it does not contain pits.
Gold or silver is used for the reflective layer in a CD-R instead of the standard aluminum found in CD- ROM and CD-A due to the improved environmental stability of these materials compared with aluminum. The CD-R reflective layer is placed on top of an organic dye polymer to form a hybrid laser-writable surface. When the dye polymer on a CD-R is heated by the laser during the write phase, a physical change occurs which will exhibit the same optical characteristics as a molded pit on a CD-ROM.
Until recently there were only two types of dyes used for CD-R - cyanine (pale-green tinge) and phtalocyanine (yellow). A recent third is metal-chelate dyes comprising azo compounds (very deep blue). The life expectancy of a CD-R under normal office conditions depends on the type of dye used. Phthalocyanine is considered to be the most stable over time (shelf life 100-300 years). Cyanine ranges from 10-100 years and has a greater tolerance for variations in laser power. However, all organic dyes used in CD-R media are susceptible to degradation by prolonged exposure to ultraviolet light. Azos are
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