Basic matters

2.1 Terms and symbols

(1) Definition of terms

Table 2.1 shows the definitions of the terms used.

Table 2.1 Definition of terms

the term	meaning
sector	A basic unit of data handled by a CD block. (Fixed at 2352 bytes) The sector size and structure follow the format of the CD-ROM.
stream	A logically continuous flow of data that is distinguished by sector headers and subheaders.
CD buffer	A buffer in a CD block that stores sector data.
CD buffer size	The size of the CD buffer in sectors.
Buffer partition	A CD buffer divided into multiple logical partitions. It can be regarded as a logical element that stores and retrieves streams.
Buffer partition size	The size of the buffer partition in sectors.
Sector position	The location of the sector within the buffer partition. (Sector unit position) It takes a value from 0 to (buffer partition size -1). The sector of the buffer partition is accessed by using the sector position as a key.
Aperture	A logical element that separates streams according to set conditions.
selector	A logical element that selects a stream, consisting of an aperture and a buffer compartment. A stream selection circuit can be constructed with a selector.
device	A logical device that generates and absorbs streams such as CD-ROM and MPEG. Stream selection processing is possible by connecting a device to the above circuit.
connector	Terminals for connecting apertures, buffer compartments, and devices.
Frame address (FAD)	A numbered frame by frame, with the absolute time 00:00:00 on the CD as 0. It corresponds to absolute time and one-to-one. Access the CD block using the frame address as the key, not the absolute time. (Both CD-ROM and CD-DA)
Logical sector number (LSN)	A numbered sector (frame) unit is continuously numbered with the absolute time 00:02:00 on the CD as 0. Logical sector number = frame address -150 (for 2 seconds). It is used for the information in the directory record (ISO9660).
File information	Directory record information held to access files. FAD at the beginning of the file, file size, unit size, gap size, There are file numbers and attributes.
File identifier	A sequence number in the directory to identify the file. It takes a value from 0 to (number of directory records-1). However, 0: indicates your own directory and 1: indicates the parent directory.

(2) List of symbols and abbreviations

Table 2.2 List of symbols and abbreviations

Symbols / abbreviations	meaning	explanation
Adr	address	address
BCD	binary coded decimal	Binary coded decimal
bn, bufno	buffer no.	Buffer partition number
bufnum	buffer numbers	Total number of buffer partitions
CI	coding information	Coding information
CN	channel no.	Channel number
Ctrl	control	Control
dst	destination	Copy / move destination
fad	frame address	Frame address
fasnum	fad sector numbers	Number of frame address sectors
fid	file identifier	File identifier
fln, filtno	filter no.	Aperture number
FN	file no.	File number
LSB	least significant bit	Lesi bit
MSB	most significant bit	Most significant bit
ply	play parameter	Playback parameters
pos	position parameter	Positional parameters
SM	submode	Submode
sct	sector	sector
ses	session information	Session information
sesno	session no.	Session number
snum	sector numbers	Number of sectors (when specifying the sector range of the partition)
sp, spos	sector position	Sector position (when specifying the sector range of the partition)
src	source	Copy / move destination
stat	CD status information	CD status information
subh	subheader condition	Subheader condition for aperture
TNO	track no.	Track number (song number)
toc	TOC information	TOC information
txwnum	transfer word numbers	Number of transfer words (data transfer size per word)
X, idx	index	Index number
word	word	word. A unit of length of 2 bytes (16 bits).

(3) Numerical notation

For binary numbers, add "B" at the end. (Example: Decimal number 5 is written as 101B.)
Hexadecimal numbers have an "H" at the end. (Example: The decimal number 255 is written as FFH.)
However, hexadecimal numbers in C language programs are expressed in the C language specifications (0x).

(4) Handling of BCD

As a general rule, BCD is not used for parameters. All numerical values recorded on the CD such as track numbers in BCD are also converted to binary values and exchanged.

(5) C language identifier

The CD communication interface uses identifiers that begin with CD or Cd. Applications should be careful not to collide with these identifiers.

2.2 Disk layout

(1) Track layout

Figure 2.1 shows the relationship between the track structure and the access key that specifies the position on the disk.

Figure 2.1 Relationship between track structure and access keys

(2) Multi-session layout

Figure 2.2 Multi-session layout