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Compaq COBOL for OpenVMS VAX and Compaq COBOL Compatibility and Migration
B.4 Compaq COBOL and Compaq COBOL for OpenVMS VAX Behavior Differences
• There is a difference between Compaq COBOL for OpenVMS VAX and
Compaq COBOL in the enforcement of the general rule that name conflicts
should be avoided, including names used for COPY libraries. The Compaq
COBOL for OpenVMS VAX compiler does not enforce this rule in some cases,
including COPY and PROGRAM-ID. Hence a program that compiles without
error on Compaq COBOL for OpenVMS VAX might result in a NAMCLASS
error on Compaq COBOL, as follows:
%COBOL-E-NAMCLASS, Multiply defined name - name used in more than one
user-defined word class at line number . . .
To avoid the error, you should either change the conflicting name or make it a
literal by putting it in quotation marks, for example:
COPY "LIBRARY-FILE" FROM COPYLIB.
B.4.7 Storage for Double-Precision Data Items
On OpenVMS, the difference in storage format of D_floating items between the
VAX and Alpha architectures produces slightly different answers when validating
execution results. The magnitude of the difference depends upon how many
D-float computations and stores the compiler has performed before outputing the
final answer. This behavior difference may cause some difficulty if you attempt to
validate output generated by your program running on OpenVMS Alpha systems
against output generated by OpenVMS VAX systems when outputting COMP-2
data to a file. ♦
Only IEEE floating point is available on Windows NT and on the Tru64 UNIX
operating system. ♦
For information about storage format for floating-point data types, see the Alpha
Architecture Reference Manual, available from Digital Press.
B.4.8 File Status Values
Compaq COBOL and Compaq COBOL for OpenVMS VAX return different
file status values when you open a file in EXTEND mode and then try to
REWRITE it. For this undefined operation, Compaq COBOL returns File Status
49 (incompatible open mode), while Compaq COBOL for OpenVMS VAX returns
File Status 43 (no previous READ).
B.4.9 RMS Special Registers (OpenVMS)
There are some differences in the behavior of RMS Special Registers that will be
experienced depending on your platform.
Loading Differences
At run time Compaq COBOL for OpenVMS Alpha and Compaq COBOL for
OpenVMS VAX update the values for the RMS special registers differently for
some I/O operations. The Compaq COBOL run-time system checks for some
I/O error situations before attempting the RMS operation. In those situations,
the Compaq COBOL run-time system does not attempt an RMS operation and
the RMS special register retains its previous value. The Compaq COBOL for
OpenVMS VAX run-time system performs all RMS operations without any prior
checking of the I/O operation. As a result, the run-time system always updates
the values for the RMS special registers for each I/O operation.
Compaq COBOL for OpenVMS VAX and Compaq COBOL Compatibility and Migration B–21