2.4. Graphical display of programs
Following are excerpts from the Unofficial DVD specifications Guide 2.2 ebook.

This document uses the following convention and graphical symbols to display a program representing its data structure as defined by the DVD specifications.


A program is simply an 8-bit pointer in a program chain (PGC) that points to a group of cells. A program may or may not be defined as a chapter. A program starts from 1 and can have a maximum value of 255 in each PGC. To clarify some complex examples, a text label such as "Program 1" is used instead of the program number. The group of cells which the program points to is displayed below its icon as shown above.


If a program is defined as a chapter, the chapter number is displayed as a label on the left side of the program icon. A program may have up to 255 cells. A cell within a program having no cell command is seamless by default.


The above illustration shows three programs. Program 1 and 3 are defined as the entries of chapter 1 and chapter 2, respectively.