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Managing Memory and Data Access
16.4 Using Alignment Directives, Qualifiers, and Flags
Example 16–1 Using *DC SET ALIGNMENT Directives
.
.
1
.
*DC SET ALIGNMENT
2
01 comp-group.
02 cg-x1 pic x.
02 cg-c1 pic 9(1) comp.
*DC SET NOALIGNMENT
3
01 comp-group-2.
02 cg-x2 pic x.
02 cg-c2 pic 9(1) comp.
*DC END-SET ALIGNMENT
4
01 comp-group-3.
02 cg-x3 pic x.
02 cg-c3 pic 9(1) comp.
*DC END-SET ALIGNMENT
5
01 comp-group-4.
02 cg-x4 pic x.
02 cg-c4 pic 9(1) comp.
1
Initially, OpenVMS VAX compatible alignment is specified either by
NOALIGNMENT or the absence of ALIGN on the compile command.
2
The SET ALIGNMENT directive specifies alignment along natural
boundaries, superseding the initial OpenVMS VAX compatible alignment.
3
The SET NOALIGNMENT directive specifies VAX compatible alignment; data
is now byte-aligned.
4
The END-SET ALIGNMENT directive terminates the alignment specified
with the previous SET directive (
3
SET NOALIGNMENT). Alignment is once
again along the natural boundaries as specified by
2
, the SET ALIGNMENT
directive.
5
This END-SET ALIGNMENT directive terminates the alignment specified
with the original directive (
2
SET ALIGNMENT). Alignment is now
OpenVMS VAX compatible as specified by the default command-line option.
16.4.3 Comparing Alignment Directive Effects
The alignment examples that follow illustrate the following important points:
• Compaq COBOL for OpenVMS VAX and Compaq COBOL align 01 (and 77)
data items along different boundaries, as follows:
Compaq COBOL for OpenVMS VAX aligns 01 data records and items
along longword boundaries. It byte-aligns all other fields unless SYNC
has been specified.
Compaq COBOL aligns 01 records and items along quadword boundaries.
It byte-aligns all other fields unless SYNC or the alignment option has
been specified.
16–8 Managing Memory and Data Access