TACL Reference Manual

Variables
HP NonStop TACL Reference Manual—429513-018
4-20
Declaring FILLER Bytes
structure-body
contains the declarations that define the substructure.
Considerations
•
You can nest substructures to any practical level. For additional information on
substructure alignment, see Declaring a Structure Body on page 4-13.
•
TACL treats a data item declared without bounds as though it had been declared
with bounds (0:0, which is one byte long).
Declaring FILLER Bytes
A FILLER byte provides a placeholder for structure data or space that your program
does not use. TACL aligns some items on word boundaries; you can use FILLER bytes
to control the alignment of data.
The syntax for the FILLER declaration is:
FILLER num;
num
is a number in the range 1 to 5000 that specifies the number of bytes of filler.
FILLER declarations contribute to more readable TACL programs. For example, you
can use FILLER bytes:
•
To define data that appears in a structure but is not used by your program
•
To document word-alignment padding bytes that would be inserted by TACL
•
To provide placeholders for unused space
You can access a FILLER item only by accessing a structure containing it; if you do
access this structure, TACL treats the FILLER item as type CHAR.
Example
This example shows sample FILLER declarations:
[#DEF sample STRUCT
BEGIN
CHAR byte (0:2);
FILLER 1; == Documents word-alignment pad byte
INT word1;
INT word2;
FILLER 30; == Placeholder for unused space
INT2 integer32;
END;
]