IBM OS/390 User Manual

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Chapter 16. FORTRAN
16.1 VS  FORTRAN in OS/390
VS FORTRAN is the compiler and library to use on OS/390. VS FORTRAN
expands greatly on what you can do with FORTRAN in accessing system
services and/or hardware features. If you have used VS FORTRAN on VSE, you
may be aware of the extensions that VS FORTRAN provides over DOS FORTRAN,
such as execution time dynamic commons, compile-time included source files,
asynchronous I/O, and level 66 language compatibility. VS FORTRAN has
multitasking on OS/390, and the Version 2 product offers programming
enhancements such as structured programming constructs, long variable names,
an Intercompilation Analyzer, and an interactive full screen debugger. In Version
2 Release 3, data-in-virtual support and dynamic file allocation are available. The
Version 2 product also supports the IBM 3090 vector hardware, and it also
conforms to the SAA Common Programming Interface (CPI).
16.2 FORTRAN Conversion Considerations
The conversion to OS/390 means that some changes are needed to certain DOS
FORTRAN programs. First, the OPSYS routine is no longer supported. The I/O
services and more are supplied in Version 2 Release 3 with dynamic file support.
The overlay support provided by OPSYS is no longer needed, because now
larger programs are supported in the 2 Gigabyte address spaces supported by
OS/390. Options that were used before to control compilation are now handled in
part by cataloged procedures and in part by the compiler options VS FORTRAN
now recognizes. VS FORTRAN also now allows execution time options to control
the running of your production programs.
Although recoding of programs is not necessary except for routines using
OPSYS, the benefits to your programs can be measured in increased
performance due to the many optimization levels the compiler provides.
Exploitation is available to recompiled programs so that they may now run above
the 16MB line. Access to the vector hardware is available through recompilation
as is access to new operating system features.
 Copyright IBM Corp. 1998 
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