How to read the syntax diagrams

Purpose

This section describes how to read the syntax diagrams used in this book.

Read the diagrams from left-to-right, top-to-bottom, following the main path line. Each diagram begins on the left with double arrowheads (►►) and ends on the right with two arrowheads facing each other (►◄).
```
>>-| Syntax Diagram |------------------------------------------><
```

If a diagram is longer than one line, the first line ends with a single arrowhead (►) and the second line begins with a single arrowhead.


>>-| First Line |----------------------------------------------><


>>-| Second Line |---------------------------------------------><

Required operands and values appear on the main path line.
```
>>-REQUIRED_OPERAND--------------------------------------------><
```
You must code required operands and values.

If your choices are greater than one, the choices are stacked vertically in alphanumeric order.
```
>>-+-REQUIRED_OPERAND_OR_VALUE_1-+-----------------------------><
   '-REQUIRED_OPERAND_OR_VALUE_2-'   
```

Optional operands and values appear below the main path line.


>>-+---------+-------------------------------------------------><
   '-OPERAND-'

You can choose not to code optional operands and values.

If your choices are more than one, they are stacked vertically in alphanumeric order below the main path line.


>>-+--------------------+--------------------------------------><
   +-OPERAND_OR_VALUE_1-+   
   '-OPERAND_OR_VALUE_2-'

An arrow returning to the left above an operand or value on the main path line means that the operand or value can be repeated. The comma means that each operand or value must be separated from the next by a comma.
```
   .-,------------------.   
   V                    |   
>>---REPEATABLE_OPERAND-+--------------------------------------><
```

An arrow returning to the left above a group of operands or values means that more than one can be selected, or a single one can be repeated.


>>-+---------------------------------------+-------------------><
   | .-,---------------------------------. |   
   | V                                   | |   
   '---+-REPEATABLE_OPERAND_OR_VALUE_1-+-+-'   
       '-REPEATABLE_OPERAND_OR_VALUE_2-'

A word in all uppercase is an operand or value you must spell exactly as shown. In this example, you must code OPERAND.
Note: VTAM® commands are not case-sensitive. You can code them in uppercase or lowercase.
```
>>-OPERAND-----------------------------------------------------><
```
If an operand or value can be abbreviated, the abbreviation is discussed in the text associated with the syntax diagram.
If a diagram shows a character that is not alphanumeric (parentheses, periods, commas, and equal signs), you must code the character as part of the syntax. In this example, you must code OPERAND=(001,0.001).
```
>>-OPERAND--=--(--001--,--0.001--)-----------------------------><
```
If a diagram shows a blank space, you must code the blank space as part of the syntax. In this example, you must code OPERAND=(001 FIXED).
```
>>-OPERAND--=--(--001-- --FIXED--)-----------------------------><
```

Default operands and values appear above the main path line. VTAM uses the default if you omit the operand entirely.


   .-DEFAULT-.   
>>-+---------+-------------------------------------------------><
   '-OPERAND-'

A word appearing in all lowercase italics is a variable. Where you see a variable in the syntax, you must replace it with one of its allowable names or values, as defined in the text.
```
>>-variable----------------------------------------------------><
```
References to syntax notes appear as numbers enclosed in parentheses above the line. Do not code the parentheses or the number.
```
           (1)   
>>-OPERAND-----------------------------------------------------><
```
Notes:
1. An example of a syntax note.
Some diagrams contain syntax fragments; these serve to break up diagrams that are too long, too complex, or too repetitious. Syntax fragment names appear in mixed case and are shown in the diagram and in the heading of the fragment. The fragment is placed below the main diagram.
```
>>-| Reference to Syntax Fragment |----------------------------><
```
```
Syntax Fragment

|--1ST_OPERAND--,--2ND_OPERAND--,--3RD_OPERAND------------------|
```