cdrom.4 (2010 09)

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cdrom(4) cdrom(4)

NAME

cdrom - CD-ROM background information

DESCRIPTION

This manpage provides general information on existing CD-ROM standards, terminology, data layout,

and levels of support. More detailed information is available in the standard documents listed in SEE

ALSO.

Not all topics discussed here are supported in the current HP-UX release. Refer to the DEPENDENCIES

section for details about the contents of the current release.

Standard Formats

Currently, two standard formats are deﬁned for CD-ROM.

The High Sierra Group (HSG) standard was produced by the CD-ROM Ad Hoc Advisory Committee, and

is documented in a publication entitled The Working Paper for Information Processing − Volume and File

Structure of Compact Read Only Optical Discs for Information Interchange . This document is available

from the National Information Standards Organization (NISO).

The second standard, which evolved from the HSG standard, was produced by the International Organi-

zation for Standardization (ISO). This standard is documented in a publication entitled Information Pro-

cessing − Volume and File Structure of CD-ROM for Information Interchange , reference number ISO

9660: 1988 (E).

Data Layout

The data layout on a CD-ROM can be represented as follows:

System Area - 32 kilobytes

Volume Descriptor

Volume Descriptor Terminator

Path Table

Directory and File Data

There are typically four sections in the CD-ROM data (indicated by double horizontal lines in the table

above): Only the ﬁrst two sections must occur in the order shown above.

The System Area consists of the ﬁrst sixteen 2048-byte blocks on the media. The contents of this section

are not speciﬁed by either standard; here, the creator of the CD-ROM can put data that is relevant to the

system for which the CD-ROM is intended.

The Volume Descriptor typically contains one primary volume descriptor and zero or more supplemen-

tary volume descriptors. Each volume descriptor is 2048 bytes in length, and describes the attributes and

structure of a directory hierarchy on the CD-ROM. The list of volume descriptors is terminated by one or

more volume descriptor terminators. A volume descriptor terminator is also 2048 bytes in length,

and simply signals the end of the volume descriptor section.

The Path Table contains all the path tables for all directory hierarchies on the CD-ROM. Path tables do

not have to be constrained to this section of the CD-ROM data, but can be interspersed with Directory

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (4 pages)

PAGE 1
cdrom(4) cdrom(4) NAME cdrom - CD-ROM background information DESCRIPTION This manpage provides general information on existing CD-ROM standards, terminology, data layout, and levels of support. More detailed information is available in the standard documents listed in SEE ALSO. Not all topics discussed here are supported in the current HP-UX release. Refer to the DEPENDENCIES section for details about the contents of the current release.
PAGE 2
cdrom(4) cdrom(4) and File Data (described below) to minimize seek times. The Directory and File Data contains data for all directory hierarchies on the CD-ROM and, as described above, can be made noncontiguous by the occasional inclusion of a path table. Volumes and Directory Hierarchies A volume is a single physical CD-ROM. A directory hierarchy is a hierarchical file system written on a volume.
PAGE 3
cdrom(4) cdrom(4) numerical values are recorded most-significant-byte-first. One of each type of path table is required by both standards. The ISO standard allows for one additional optional copy of each type of path table, while the HSG standard allows for up to three additional optional copies of each type. Additional copies of path tables are useful for redundancy or seek time minimization.
PAGE 4
cdrom(4) cdrom(4) Level 1 The system is permitted to ignore supplementary volume descriptors, their associated path tables, and all directory and file data associated with them. Level 2 No restrictions apply. In all cases, receiving systems must fulfill the receiving system requirements specified in section 10 of the ISO standard (no equivalent section exists for HSG). Interchange levels provide a way to specify the data structure and complexity that exists on a CDROM.