Green Book
Specification for CD-I.
High Sierra/High Sierra Format
The Hotel in Nevada, USA where in 1985 the foundation was laid for determining the file systems for CDs. The efforts of the group which came to be known as the
“High Sierra Group” led to the standard ISO 9660, the most common file system for CDs. A CD that conforms to this standard is at times still referred to as a “High
Sierra” CD. The original High Sierra format has almost died out; as a rule, ISO 9660 is used instead.
Image File
see physical image.
ISO 9660
ISO 9660 describes the requirements a CD file system has to fulfil. This allows a CD to be used universally. Only the capital letters from A to Z, the digits 0 to 9 and
the underscore symbol are permitted for file and directory names. Diacritical marks (Ä, Ö, Ü), foreign characters and punctuation marks (ß, ?, ! etc.) as well as
hyphens are not permitted. The filename can have a max. of 8 characters, the extension only up to 3. The filename must be at least one character in length, for
example ‘A’. A version number (1 to 32767) can be appended (for example ‘A.B;1’). A maximum directory hierarchy of eight levels is permitted whereby the root is
considered the first level. The ISO 9660 employs specifications of the High Sierra Group and is for that reason also called the High Sierra format. There are also
other file systems ( for example, Joliet for Win95 or HFS for Apple Macintosh) which, however, can only be recognised on these types of systems.
Joliet
CD file system that supports long filenames and can be used under Windows .95. For full compatibility to DOS, an ISO 9660 file system must be created. This is a
part of the complete Joliet system.
Lead-In
The lead-in is a data area at the beginning of a CD-R session. This area contains the directory (table of contents TOC) of a session. The lead-in is written together
with the lead-out of a session. Every lead-in uses 4500 sectors (approx. 9 MB) on the CD.
Lead-Out
The lead-out marks the physical end of a session and does not contain any data. It is written together with the lead-in. The first lead-out of a CD uses 6750
sectors (approx. 13 MB), all following ones 2250 sectors (approx. 4 MB).
Mixed Mode CDs
A CD which contains both computer data and audio data is known as a Mixed Mode CD. The computer data is stored on the first track. All the other tracks
contain audio data. Modern CD players do not reproduce the first track. Older models, however, will try to “play back” the computer data which, in some cases,
can cause damage to the stereo system.
Multisession
A data CD can be written in several sessions. This must be set accordingly while writing. Typical instances where multisession CDs are used are regular backups
and Photo CDs which are gradually filled up.
Multitasking
Windows allows you to open several windows simultaneously. This is known as multitasking. When writing CDs, only the writing software window should be open
(running), for full and exclusive use of the computer’s resources. Screen savers, modems and network functions should be deactivated as they all use up
computer resources which, in extreme cases, may disrupt the writing process.
On-the-Fly
Writing directly onto a CD-R without creating a physical image. If it is not possible to gain fast access to the source files, the writing process cannot be carried
out successfully (“Buffer Underrun”). Only small amounts of data with simple data structure should be written On-the-Fly. The source files should be copied onto
the hard disk.
Orange Book
The Orange Book contains the specifications for CD-R (recordable CDs) & CD-RW (rewritable CDs). These CDs contain no information other than some special
data (ATIP Codes), and they can be written according to any of the other colour book standards. Manufacturers of blank CDs have to abide by the regulations in
the Orange Book.
Packet Writing
A method of writing CDs which makes it possible to write data in smaller blocks (packets) than is the case with the usual Track-at-Once or Disc-at-Once
procedures. This procedure allows data blocks to be written onto the CD-R without having to finish the particular track. A further advantage of Packet Writing is
the simple updating of existing files. Data can be simply added without having to rewrite the file directory each time.
Physical Image
Before writing a CD, an identical 1:1 copy of the new CD is created on the hard disk. The file will be the size of the record (i.e. up to 650 MB). Creating a physical
image requires a certain amount of processing which is not necessary for writing. For the writing procedure, only the file to be written is transferred. The CPU
load ( C entral P rocessing U nit) remains small and cannot cause disruption. When creating several identical CDs, the physical image is less time-consuming
because the processing mentioned above only has to be carried out once.
“Raw” Files
A “raw” file contains data which is already in CD format. It can be directly written without further modification. One “raw” file corresponds to one track. For
example, a “raw” audio file can be used as the contents of one CD-DA track. Image files are “raw” files.
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