vRequired items appear on the horizontal line (the main path).
 STATEMENT required_item 
vOptional items appear below the main path.
 STATEMENT
optional_item

vIf you can choose from two or more items, they appear vertically, in a stack.
If you must choose one of the items, one item of the stack appears on the main path.
 STATEMENT required_choice1
required_choice2

If choosing is optional, the entire stack appears below the main path.
 STATEMENT
optional_choice1
optional_choice2

vIf one of the items is the default, it appears above the main path and the remaining choices are shown
below.
 STATEMENT
default_choice
optional_choice
optional_choice

vAn arrow returning to the left above the main line indicates an item that can be repeated.
 STATEMENT repeatable_item 
A repeat arrow above a stack indicates that you can repeat the items in the stack.
vA set of vertical bars around an item indicates that the item is a fragment, a part of the syntax diagram
that appears in greater detail below the main diagram.
 STATEMENT fragment 
fragment:
expansion_provides_greater_detail
vKeywords appear in uppercase (for example, PARM1). They must be spelled exactly as shown but can be
specified in any case. Variables appear in all lowercase letters (for example, parmx). They represent
user-supplied names or values.
vIf punctuation marks, parentheses, arithmetic operators, or such symbols are shown, you must enter
them as part of the syntax.
Introduction
Chapter 11. Introduction 107