Compaq Fortran

User Manual for
Tru64 UNIX and Linux Alpha Systems

Order Number: AA-Q66TD-TE

This manual provides information about the Compaq® Fortran (formerly DIGITAL® Fortran 90) program development and run-time environment on Compaq Tru64^tm UNIX® (formerly DIGITAL UNIX) and Linux® Alpha systems.

It describes compiling, linking, running, and debugging Compaq Fortran programs, performance guidelines, run-time I/O and error-handling support, data types, numeric data conversion, calling other procedures and library routines, and compatibility with Compaq Fortran 77 (formerly DEC Fortran). It also describes the f90 command options needed to develop Compaq Fortran programs for parallel execution on Tru64 UNIX using High Performance Fortran features.

Revision/Update Information: This manual supersedes the previous version of this manual, the DIGITAL Fortran 90 User Manual for DIGITAL UNIX Systems, order number AA-Q66TC-TE.

Software Version: Compaq Fortran for Tru64 UNIX Systems: Version 5.3 or higher
Compaq Fortran for Linux® Alpha Systems: Version 1.0 or higher

Compaq Computer Corporation
Houston, Texas

First Printing, June 1994 First Revision, March 1996 Second Revision, March 1998 Third Revision, December 1999

Compaq Computer Corporation makes no representations that the use of its products in the manner described in this publication will not infringe on existing or future patent rights, nor do the descriptions contained in this publication imply the granting of licenses to make, use, or sell equipment or software in accordance with the description.

Possession, use, or copying of the software described in this publication is authorized only pursuant to a valid written license from Compaq or an authorized sublicensor.

Compaq, the Compaq Logo, DEC, DECnet, DIGITAL, VAX, and VMS are registered in the U.S. Patent and Trademark Office.

AlphaGeneration, AlphaServer, DEC Fortran, DEC FUSE, DECwindows, OpenVMS, Tru64, ULTRIX, and VAX FORTRAN are trademarks of Compaq Computer Corporation.

Microsoft, NT, and Windows are either trademarks or registered trademarks of Microsoft Corporation in the United States and other countries.

CRAY is a registered trademark of Cray Research, Inc.
Hewlett-Packard and HP-UX are registered trademarks of the Hewlett-Packard Company.
IBM is a registered trademark of International Business Machines Corporation.
IEEE is a registered trademark of the Institute of Electrical and Electronics Engineers, Inc.
KAP is a registered trademark of the Kuck and Associates, Inc.
Linux is a trademark of Linus Torvalds.
OpenMP and the OpenMP logo are trademarks of OpenMP Architecture Review Board.
OSF, OSF/1, and OSF/Motif are registered trademarks of the Open Software Foundation, Inc.
RISC System/6000 is a registered trademark of International Business Machines Corporation.
Sun is a registered trademark of Sun Microsystems, Inc.
System\370 is a registered trademark of International Business Machines Corporation.
TotalView is a trademark of Dolphin Interconnect Solutions.
UNIX is a registered trademark in the United States and other countries licensed exclusively through X/Open Company Ltd.

Other product names mentioned herein may be trademarks of respective companies.

Cover graphic, image: CERN, European Laboratory for Particle Physics: ALICE detector on CERN's future accelerator, the LHC, Large Hadron Collider.

ZK6325

Contents Index

Preface

This manual describes the Compaq Fortran compiler command, compiler, and run-time environment. This includes how to compile, link, execute, and debug Compaq Fortran nonparallel programs using the Compaq Tru64 UNIX operating system on Alpha hardware.

This manual does not cover running, debugging, and profiling programs that execute in parallel using High Performance Fortran (HPF) features (requires Compaq MPI, part of the Compaq Parallel Software Environment product).

Intended Audience

This manual makes the following assumptions about you, the reader:

You already have a basic understanding of the Fortran 95/90 language. Tutorial Fortran 95/90 language information is widely available in commercially published books (see the online release notes or the Preface of the Compaq Fortran Language Reference Manual).
You are familiar with the operating system shell commands used during program development and a text editor, such as emacs or vi . Such information is available in your operating system documentation set or commercially published books.
You have access to the Compaq Fortran Language Reference Manual, which describes the Compaq Fortran language.
If you will be developing programs for parallel execution using the Compaq Parallel Software Environment, you have access to the Parallel Software Environment documentation set (see "Associated Documents" later in this Preface).

Structure of This Document

This manual consists of the following chapters and appendixes:

Chapter 1 introduces the programmer to the Compaq Fortran compiler, its components, and related commands.
Chapter 2 explains how to compile and link Compaq Fortran source programs, previously compiled module files, object files, and routines written in other supported programming languages, such as C.
Chapter 3 describes the Compaq Fortran compiler command-line options in detail.
Chapter 4 describes using the Compaq Ladebug debugger to debug Compaq Fortran nonparallel programs. (For information related to debugging parallel High Performance Fortran (HPF) programs, see the Compaq Parallel Software Environment documentation.)
Chapter 5 describes ways to improve Compaq Fortran run-time performance for nonparallel programs, including general software environment recommendations, appropriate compiler command-line options, data alignment, efficiently performing I/O and array operations, other efficient coding techniques, profiling, and optimization. (For information on improving the performance of parallel HPF programs, see Compaq Parallel Software Environment documentation.)
Chapter 6 describes how to use parallel compiler directives in Compaq Fortran programs to generate code that executes in parallel.
Chapter 7 provides information on Compaq Fortran I/O, including statement forms, file organizations, I/O record formats, access modes, logical unit numbers, and efficient use of I/O.
Chapter 8 lists run-time messages and describes how to control certain types of I/O errors and signal-handling considerations.
Chapter 9 describes native Compaq Fortran Alpha data types, including their numeric ranges, representation, and floating-point exceptional values. It also discusses the intrinsic data types used with numeric data.
Chapter 10 describes how to access unformatted files containing numeric little endian and big endian data different than the format used in memory.
Chapter 11 describes the Compaq Fortran language interface, passing arguments, calling between Compaq Fortran and Compaq Fortran 77, and calling between Compaq Fortran and C.
Chapter 12 lists and briefly describes the Section 3f interface routines, which include some routines specifically designed for the Compaq Fortran environment on Compaq Tru64 UNIX systems.
Chapter 13 describes the Compaq Extended Math Library (CXML), including how to call and link CXML routines.
Appendix A provides compatibility information for those porting Compaq Fortran 77 (formerly DEC Fortran) applications and Compaq Fortran OpenVMS^tm applications, including an overview of Compaq Fortran 77 and Compaq Fortran extensions supported on the various platforms. It:
- Describes language differences between Compaq Fortran and Compaq Fortran 77 on Tru64 UNIX systems
- Describes Compaq Fortran extensions for OpenVMS systems that are not supported by this version of Compaq Fortran on Compaq Tru64 UNIX Systems
- Provides information on porting OpenVMS data files to Compaq Tru64 UNIX systems.
Appendix B lists the Compaq Fortran environment variables recognized at compile-time and run-time.
Appendix C describes the source listing formats supported by Compaq Fortran.
Appendix D summarizes the library routines available for use with directed parallel decomposition.

The appendix formerly titled "Parallel Compiler Directives Reference Material" is no longer in this manual. The contents of this appendix are in the Compaq Fortran Language Reference Manual.

Associated Documents

The following documents may also be useful to Compaq Fortran programmers:

Compaq Fortran Language Reference Manual
Describes the Compaq Fortran 95/90 source language for reference purposes, including the format and use of statements, intrinsic procedures, and other language elements. Compaq extensions to the Fortran 95 standard are identified by blue-green color in the printed document and HTML versions. It also provides an overview of new Fortran 90 features (not available in FORTRAN-77). Language differences among Compaq Fortran platforms are identified.
Compaq Fortran Installation Guide for Tru64 UNIX Systems
Explains how to install Compaq Fortran on the Compaq Tru64 UNIX operating system, including prerequisites and requirements.
To install Compaq Fortran on Linux Alpha systems, refer to the letter with your kit.
Compaq Fortran online release notes
Provide more information on this version of Compaq Fortran, including known problems and a summary of the Compaq Fortran run-time error messages.
(TU*X ONLY) The online release notes are located in:
/usr/lib/cmplrs/fort90

(TU*X ONLY) To view this file, use the more command (or view ) on a system where Compaq Fortran is installed:
% more /usr/lib/cmplrs/fort90/relnotes
(L*X ONLY) The online release notes are located in:
/usr/doc/cfal-1.n

The value of n in this location comes from the list 0, 1, 2, ...
(L*X ONLY) To view this file, use the more command (or view ) on a system where Compaq Fortran is installed:
% more /usr/doc/cfal-1.0/README
To initiate a search within more , type a slash (/) followed by the appropriate topic. For information about using the more command, see more(1).
Compaq Fortran online reference pages
Describe the Compaq Fortran software components, including f90(1) (Tru64 UNIX systems) or fort(1) (Linux systems), fpr(1), fsplit(1), intro(3f), numerous Fortran library routines listed in intro(3f), and numerous parallel Fortran library routines listed in intro(3hpf).
Compaq Parallel Software Environment documentation
(TU*X ONLY) Explains both the Compaq Parallel Software Environment (PSE) product (including Compaq MPI) and the High Performance Fortran (HPF) programming language.
Parallel Software Environment online release notes
Provide the most recent information on the installed version of the Parallel Software Environment.
Compaq Tru64 UNIX operating system documentation
The operating system documentation set includes reference pages for operating system components and a programmer's subkit, in which certain documents describe the commands, tools, libraries, and other aspects of the programming environment:
- For programming information, see the Compaq Tru64 UNIX Programmer's Guide and the Compaq Tru64 UNIX Using Programming Support Tools.
- For performance information, see the Compaq Tru64 UNIX System Tuning and Performance.
- For an overview of Compaq Tru64 UNIX documentation, see the Compaq Tru64 UNIX Reader's Guide.
Other layered product documentation
If you are using a programming-related layered product package from Compaq, consult the appropriate documentation for the layered product package for use of that product.

Platform Labels

A platform is a combination of operating system and central processing unit (CPU) that provides a distinct environment in which to use a product (in this case, a language). This manual contains information for both Compaq Tru64 UNIX on Alpha systems and Linux on Alpha systems --- unless otherwise labeled for a specific platform as shown in Table 1.

Table 1 Platform Labels
TU*X Applies to Tru64 UNIX on Alpha processors

L*X Applies to Linux on Alpha processors

**Table 1 Platform Labels**
TU*X	Applies to Tru64 UNIX on Alpha processors
L*X	Applies to Linux on Alpha processors

For example, the shcom_connect library routine in Table 12-2 is labeled "(TU*X ONLY)", so this routine is only valid for Tru64 UNIX operating systems on Alpha processors.

Sending Compaq Your Comments on This Manual

Compaq welcomes your comments on this or any other Compaq Fortran manual. You can send comments to us in the following ways:

Internet electronic mail: fortran@compaq.com
FAX: 603-884-0120 Attn: Languages Documentation, ZKO2-3/N30

If you have suggestions for improving particular sections or find any errors, please indicate the title, order number, and section numbers. Compaq also welcomes general comments.

Communicating with Compaq

If you have a customer support contract and have comments or questions about Compaq Fortran software, you can contact our Customer Support Center (CSC), preferably using electronic means (such as DSNlink). In the United States, customers can call the CSC at 1-800-354-9000.

You may also send comments, questions and suggestions about the Compaq Fortran product to the following Internet mail address: fortran@compaq.com. Please note, however, that this address is for informational inquiries only. It is not a formal support channel.

Compaq Fortran World Wide Web Pages

If you have Internet access and a World Wide Web (WWW) browser, you are invited to view the Compaq Fortran home page, located at the following URL:

http://www.compaq.com/fortran

This Web site contains information about software patch kits, example programs, and additional product information.

Conventions Used in This Document

This manual uses the conventions listed in Table 2.

Table 2 Conventions Used in This Document
Convention Meaning

% The default user prompt is your system name followed by a right angle bracket. This manual uses a percent sign (%) to represent this prompt. The actual user prompt varies with the shell in use.

[RETURN] This symbol indicates that you must press the named key on the keyboard.

Ctrl/ x This symbol indicates that you must press the Ctrl key while you simultaneously press the key labeled x.

% pwd
/usr/usrc/jones This manual displays system prompts and responses using a monospaced font. Typed user input is displayed in a bold monospaced font.

monospaced This typeface indicates the name of a command, option, pathname, file name, directory path, or partition. This typeface is also used in examples of program code, interactive examples, and other screen displays.

cat(1) A shell command name followed by the number 1 in parentheses refers to a command reference page. Similarly, a routine name followed by the number 2 or 3 in parentheses refers to a system call or library routine reference page. (The number in parentheses indicates the section containing the reference page.) To read online reference pages, use the man command. Your operating system documentation also includes reference page descriptions.

newterm Bold type indicates the introduction of a new term in text.

variable Italic type indicates important information, a complete title of a manual, or variable information, such as user-supplied information in command or option syntax.

UPPERCASE
lowercase The operating system shell differentiates between lowercase and uppercase characters. Literal strings that appear in text, examples, syntax descriptions, and function definitions must be typed exactly as shown.

Large braces enclose lists from which you must choose one item. For example:

STATUS
DISPOSE
DISP

[ ] Square brackets enclose items that are optional. For example: BLOCK DATA [nam]

... A horizontal ellipsis means that the item preceding the ellipsis can be repeated. For example: s[,s]...

.
.
.
A vertical ellipsis in a figure or example means that not all of the statements are shown.

real This term refers to all floating-point intrinsic data types as a group.

complex This term refers to all complex floating-point intrinsic data types as a group.

logical This term refers to logical data types as a group.

integer This term refers to integer data types as a group.

Alpha
Alpha systems The terms Alpha and Alpha systems refer to the Alpha architecture or systems equipped with this 64-bit architecture.

Compaq Tru64 UNIX
Compaq Tru64 UNIX systems The terms Compaq Tru64 UNIX and Compaq Tru64 UNIX systems refer to the Compaq Tru64 UNIX (formerly DIGITAL UNIX) operating system running on Alpha processor hardware.

Fortran This term refers to language information that is common to ANSI FORTRAN 77, ANSI/ISO Fortran 95/90, and Compaq Fortran.

Fortran 95/90 This term refers to language information that is common to ANSI/ISO Fortran 95 and ANSI/ISO Fortran 90.

f90 This command invokes the Compaq Fortran compiler on Tru64 UNIX Alpha systems while the fort command invokes the Compaq Fortran compiler on Linux Alpha systems. This manual frequently uses the f90 command to indicate invoking the Compaq Fortran on both systems, so replace this command with fort if you are working on a Linux Alpha system.

fort This command invokes the Compaq Fortran compiler on Linux Alpha systems. See the previous convention for the f90 command.

Compaq Fortran 77
DEC Fortran The term Compaq Fortran 77 (formerly DEC Fortran) refers to language information that is common to the FORTRAN-77 standard and any Compaq Fortran extensions.

Compaq Fortran The term Compaq Fortran (formerly DIGITAL Fortran 90) refers to language information that is common to the Fortran 95/90 standards and any Compaq Fortran extensions.

Parallel Software Environment This term refers to an optional license and software that includes Compaq MPI, which is needed for parallel execution of programs using High Performance Fortran (HPF) constructs.

HPF This term refers to the High Performance Fortran Language.

**Table 2 Conventions Used in This Document**
Convention	Meaning
%	The default user prompt is your system name followed by a right angle bracket. This manual uses a percent sign (%) to represent this prompt. The actual user prompt varies with the shell in use.
`[RETURN]`	This symbol indicates that you must press the named key on the keyboard.
Ctrl/ x	This symbol indicates that you must press the Ctrl key while you simultaneously press the key labeled x.
`%` `pwd` `/usr/usrc/jones`	This manual displays system prompts and responses using a monospaced font. Typed user input is displayed in a bold monospaced font.
`monospaced`	This typeface indicates the name of a command, option, pathname, file name, directory path, or partition. This typeface is also used in examples of program code, interactive examples, and other screen displays.
`cat(1)`	A shell command name followed by the number 1 in parentheses refers to a command reference page. Similarly, a routine name followed by the number 2 or 3 in parentheses refers to a system call or library routine reference page. (The number in parentheses indicates the section containing the reference page.) To read online reference pages, use the `man` command. Your operating system documentation also includes reference page descriptions.
newterm	Bold type indicates the introduction of a new term in text.
variable	Italic type indicates important information, a complete title of a manual, or variable information, such as user-supplied information in command or option syntax.
UPPERCASE lowercase	The operating system shell differentiates between lowercase and uppercase characters. Literal strings that appear in text, examples, syntax descriptions, and function definitions must be typed exactly as shown.
	Large braces enclose lists from which you must choose one item. For example: STATUS DISPOSE DISP
[ ]	Square brackets enclose items that are optional. For example: `BLOCK DATA [nam]`
...	A horizontal ellipsis means that the item preceding the ellipsis can be repeated. For example: `s[,s]...`
. . .	A vertical ellipsis in a figure or example means that not all of the statements are shown.
real	This term refers to all floating-point intrinsic data types as a group.
complex	This term refers to all complex floating-point intrinsic data types as a group.
logical	This term refers to logical data types as a group.
integer	This term refers to integer data types as a group.
Alpha Alpha systems	The terms Alpha and Alpha systems refer to the Alpha architecture or systems equipped with this 64-bit architecture.
Compaq Tru64 UNIX Compaq Tru64 UNIX systems	The terms Compaq Tru64 UNIX and Compaq Tru64 UNIX systems refer to the Compaq Tru64 UNIX (formerly DIGITAL UNIX) operating system running on Alpha processor hardware.
Fortran	This term refers to language information that is common to ANSI FORTRAN 77, ANSI/ISO Fortran 95/90, and Compaq Fortran.
Fortran 95/90	This term refers to language information that is common to ANSI/ISO Fortran 95 and ANSI/ISO Fortran 90.
`f90`	This command invokes the Compaq Fortran compiler on Tru64 UNIX Alpha systems while the `fort` command invokes the Compaq Fortran compiler on Linux Alpha systems. This manual frequently uses the `f90` command to indicate invoking the Compaq Fortran on both systems, so replace this command with `fort` if you are working on a Linux Alpha system.
`fort`	This command invokes the Compaq Fortran compiler on Linux Alpha systems. See the previous convention for the `f90` command.
Compaq Fortran 77 DEC Fortran	The term Compaq Fortran 77 (formerly DEC Fortran) refers to language information that is common to the FORTRAN-77 standard and any Compaq Fortran extensions.
Compaq Fortran	The term Compaq Fortran (formerly DIGITAL Fortran 90) refers to language information that is common to the Fortran 95/90 standards and any Compaq Fortran extensions.
Parallel Software Environment	This term refers to an optional license and software that includes Compaq MPI, which is needed for parallel execution of programs using High Performance Fortran (HPF) constructs.
HPF	This term refers to the High Performance Fortran Language.

Contents

Index