TAL Programmer's Guide

Structure Layout
Using Structures
8–2 096254 Tandem Computers Incorporated
Structure Layout The structure layout is a BEGIN-END construct that contains declarations of structure
items. Table 8-2 lists structure items.
Table 8-2. Structure Items
Structure Item Description
Simple variable A single-element variable
Array A variable that contains multiple elements of the same data type
Substructure A structure nested within a structure (to a maximum of 64 levels)
Filler byte A place-holding byte
Filler bit A place-holding bit
Simple pointer A variable that contains the memory address, usually of a simple variable or
array, which you can access with this simple pointer
Structure pointer A variable that contains the memory address of a structure, which you can
access with this structure pointer
Redefinition A new identifier and sometimes a new description for a substructure, simple
variable, array, or pointer declared in the same structure
You can nest substructures within structures up to 64 levels deep. That is, you can
declare a substructure within a substructure within a substructure, and so on, for up to
64 levels. The structure and each substructure has a BEGIN-END level depending on
the level of nesting.
The following rules apply to all structure items:
You can declare the same identifier in different structures and substructures, but
you cannot repeat an identifier at the same BEGIN-END level.
You cannot initialize a structure item when you declare it. After you have
declared it, however, you can assign a value to it by using an assignment or move
statement.
The following subsections describe how to declare definition, template, referral
structures, and structure items.