Syntax notation

Throughout this book, syntax descriptions use the structure defined below.
  • 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 statement.

    The ───> symbol indicates that the statement syntax is continued on the next line.

    The >─── symbol indicates that a statement is continued from the previous line.

    The ──>< indicates the end of a statement.

    Diagrams of syntactical units other than complete statements start with the >─── symbol and end with the ───> symbol.

  • Keywords appear in uppercase letters (for example, ASPACE) or upper and lower case (for example, PATHFile). They must be spelled exactly as shown. Lower case letters are optional (for example, you could enter the PATHFile keyword as PATHF, PATHFI, PATHFIL or PATHFILE).

    Variables appear in all lowercase letters in a special typeface (for example, integer). They represent user-supplied names or values.

  • If punctuation marks, parentheses, or such symbols are shown, they must be entered as part of the syntax.
  • Required items appear on the horizontal line (the main path).
    Figure 1.
    1 INSTRUCTION  required item
  • Optional items appear below the main path. If the item is optional and is the default, the item appears above the main path.
    Figure 2.
    1! default item
    1 optional item
  • When 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.
    Figure 3.
    1 required choice1
    1 required choice2
    If choosing one of the items is optional, the whole stack appears below the main path.
    Figure 4.
    1 optional choice1
    1 optional choice2
  • An arrow returning to the left above the main line indicates an item that can be repeated. When the repeat arrow contains a separator character, such as a comma, you must separate items with the separator character.
    Figure 5.
    1 INSTRUCTION + , 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.

The following example shows how the syntax is used.

Syntax diagram

Figure 6.

1? optional item(1) INSTRUCTION(2) + , %Fragment(3)

1 operand choice1
1 operand choice2(4)
1 operand choice3
  • 1 The item is optional, anc can be coded or not.
  • 2 The INSTRUCTION keyword must be specified and coded as shown.
  • 3 The item referred to by Fragment is a required operand. Allowable choices for this operand are given in the fragment of the syntax diagram shown below Fragment at the bottom of the diagram. The operand can also be repeated. That is, more than one choice can be specified, with each choice separated by a comma. The note at the bottom of the syntax diagram indicates a restriction on the choice.
  • 4 operand choice2 and operand choice3 must not be specified together