How to read the syntax diagrams

Throughout this publication, the following structures are used in describing syntax:

Read the syntax diagrams from left to right, from top to bottom, following the path of the line.
The →→─ symbol indicates the beginning of a command.

The ─→ symbol indicates that the command syntax is continued on the next line.

The →─ symbol indicates that a command is continued from the preceding line.

The ─→← symbol indicates the end of a command.

Required items appear on the horizontal line (main path).


>>-STATEMENT--required_item------------------------------------><

Optional items appear below the main path.


>>-STATEMENT--+---------------+--------------------------------><
              '-optional_item-'

If you can choose from two or more items, they appear in a vertical 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 one of the items is optional, the entire stack appears below the main path.


>>-STATEMENT--+------------------+-----------------------------><
              +-optional_choice1-+   
              '-optional_choice2-'

If one of the optional items is the default, it appears above the main path and the remaining choices will be shown.


              .-default_choice1--.   
>>-STATEMENT--+------------------+-----------------------------><
              +-optional_choice2-+   
              '-optional_choice3-'

Keywords appear in uppercase (for example, PARM1). They must be spelled exactly as shown.
Variables appear in lowercase italics (for example, parmx). They represent user-supplied names or values.
```
>>-STATEMENT--variable-----------------------------------------><
```
An arrow returning to the left above the main line indicates an item that can be repeated.
```
              .-----------------.   
              V                 |   
>>-STATEMENT----repeatable_item-+------------------------------><
```
A repeat arrow above a stack indicates that you can make more than one choice from the stacked items, or repeat a single choice.
- A repeat arrow above a stack of keywords means that you can enter one or more of the keywords. However, each keyword can be entered only once.
- A repeat arrow above a variable means that you can enter one or more values for the variable. However, each value can be entered only once.
If punctuation marks, parentheses, arithmetic operators, or other such symbols are shown, you must enter them as part of the syntax.

Sometimes a single substitution represents a set of several parameters. For example, in the following diagram, the callout Parameter Block can be replaced by any of the interpretations of the subdiagram that is labeled Parameter Block:.


>>-STATEMENT--+-CLAUSE1-------------+--------------------------><
              '-| Parameter Block |-'   

Parameter Block

|--+-PARM1-----------+------------------------------------------|
   '-PARM2-+-PARM3-+-'   
           '-PARM4-'