DIGITAL Fortran 90

Order Number: AA--Q66TC--TE

This manual provides information about the DIGITAL Fortran 90 (formerly DEC Fortran 90) program development and run-time environment on DIGITAL UNIX (formerly DEC OSF/1) Alpha systems.

It describes compiling, linking, running, and debugging DIGITAL Fortran 90 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 DIGITAL Fortran 77 (formerly DEC Fortran). It also describes the f90 command options needed to develop DIGITAL Fortran 90 programs for parallel execution 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--Q66TB--TE.

Software Version: DIGITAL Fortran 90 Version 5.1 or higher

Digital Equipment Corporation
Maynard, Massachusetts

The information in this document is subject to change without notice and should not be construed as a commitment by Digital Equipment Corporation. Digital Equipment Corporation assumes no responsibility for any errors that may appear in this document.

The software described in this document is furnished under a license and may be used or copied only in accordance with the terms of such license.

Copyright ©1994, 1998

The following are trademarks of Digital Equipment Corporation: AXP, DEC, DEC Fortran, DEC FUSE, DECnet, DECwindows, DIGITAL, OpenVMS, ULTRIX, VAX, VAX FORTRAN, VMS, and the DIGITAL logo.

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All other trademarks and registered trademarks are the property of their respective holders.

ZK6325

This document is available on CD-ROM.

This document was prepared using VAX DOCUMENT, Version V3.2-1m.

Contents

Index

This manual describes the DIGITAL Fortran 90 compiler command, compiler, and run-time environment. This includes how to compile, link, execute, and debug DIGITAL Fortran 90 nonparallel programs using the DIGITAL UNIX (formerly DEC OSF/1) operating system on Alpha hardware.

This manual describes the program development environment that is common to DIGITAL Fortran 90 and its associated run-time Parallel Software Environment, including the f90 command options needed to develop DIGITAL Fortran 90 programs for parallel run-time execution on multiple systems. It does not cover running, debugging, and profiling programs that execute in parallel using High Performance Fortran (HPF) features (requires the DIGITAL Parallel Software Environment).

The term Parallel Software Environment refers to an optional product (license and software) that allows parallel HPF execution of programs on multiple Alpha systems running the DIGITAL UNIX operating system.

Intended Audience

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

• You already have a basic understanding of the Fortran 90 language. Tutorial Fortran 90 language information is widely available in commercially published books (see the online release notes or the Preface of the DIGITAL 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 DIGITAL Fortran Language Reference Manual, which describes the DIGITAL Fortran 90 language.
• If you will be developing programs for parallel execution using the DIGITAL 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 DIGITAL Fortran 90 compiler, its components, and related commands.
• Chapter 2 explains how to compile and link DIGITAL Fortran 90 source programs, previously compiled module files, object files, and routines written in other supported programming languages, such as C.
• Chapter 3 describes the DIGITAL Fortran 90 f90 command options in detail.
• Chapter 4 describes using the DIGITAL Ladebug debugger to debug DIGITAL Fortran 90 nonparallel programs. (For information related to debugging parallel High Performance Fortran (HPF) programs using the Parallel Software Environment, see the DIGITAL High Performance Fortran 90 HPF and PSE Manual.)
• Chapter 5 describes ways to improve DIGITAL Fortran 90 run-time performance for nonparallel programs, including general software environment recommendations, appropriate f90 command 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 DIGITAL High Performance Fortran 90 HPF and PSE Manual.)
• Chapter 6 describes how to use parallel compiler directives in DIGITAL Fortran programs to generate code that executes in parallel.
• Chapter 7 provides information on DIGITAL Fortran 90 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 DIGITAL Fortran 90 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 DIGITAL Fortran 90 language interface, passing arguments, calling between DIGITAL Fortran 90 and DIGITAL Fortran 77, and calling between DIGITAL Fortran 90 and C.
• Chapter 12 lists and briefly describes the Section 3f interface routines, which include some routines specifically designed for the DIGITAL Fortran 90 environment on DIGITAL UNIX systems.
• Appendix A provides compatibility information for those porting DIGITAL Fortran 77 (formerly DEC Fortran) applications and DIGITAL Fortran 90 OpenVMS^tm applications, including an overview of DIGITAL Fortran 77 and DIGITAL Fortran 90 extensions supported on the various platforms. It:
  • Describes language differences between DIGITAL Fortran 90 and DIGITAL Fortran 77 on DIGITAL UNIX systems
  • Describes DIGITAL Fortran extensions for OpenVMS systems that are not supported by this version of DIGITAL Fortran 90 on DIGITAL UNIX Systems
  • Provides information on porting OpenVMS data files to DIGITAL UNIX systems.
• Appendix B lists the DIGITAL Fortran 90 environment variables recognized at compile-time and run-time.
• Appendix C describes the source listing formats supported by DIGITAL Fortran 90.
• Appendix D provides reference material for parallel compiler directives.
• Appendix E summarizes the library routines available for use with directed parallel decomposition.

Associated Documents

The following documents may also be useful to DIGITAL Fortran 90 programmers:

• DIGITAL Fortran Language Reference Manual
  Describes the DIGITAL Fortran 90 source language for reference purposes, including the format and use of statements, intrinsic procedures, and other language elements. DIGITAL extensions to the Fortran 90 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 DIGITAL Fortran 90 platforms are identified.
• DIGITAL Fortran Installation Guide for DIGITAL UNIX Systems
  Explains how to install DIGITAL Fortran 90 on the DIGITAL UNIX operating system, including prerequisites and requirements.
• DIGITAL High Performance Fortran 90 HPF and PSE Manual
  Explains both the DIGITAL Parallel Software Environment (PSE) product and the High Performance Fortran (HPF) programming language. This manual:
  • Describes the installation, set up, administration, and general use of the PSE software, as well as hardware configuration for a parallel Alpha Cluster.
  • Contains a tutorial describing how to write programs using the HPF extensions to Fortran 90.
  • Describes how to run, debug, and profile HPF programs in the PSE.
• DIGITAL Fortran 90 online release notes
  Provide more information on this version of DIGITAL Fortran 90, including known problems and a summary of the DIGITAL Fortran 90 run-time error messages. The online release notes are located in:
  • /usr/lib/cmplrs/fort90/relnotes
  
  To view this file, use the more command (or view ) on a system where DIGITAL Fortran 90 is installed:

  % more /usr/lib/cmplrs/fort90/relnotes

  
  To initiate a search within more , type a slash (/) followed by the appropriate topic. For information about using the more command, see more(1).

• DIGITAL Fortran 90 online reference pages
  Describe the DIGITAL Fortran 90 software components, including f90(1), fpr(1), fsplit(1), intro(3f), numerous Fortran library routines listed in intro(3f), and numerous parallel Fortran library routines listed in intro(3hpf).
• Parallel Software Environment online release notes
  Provide the most recent information on the installed version of the Parallel Software Environment.

• DIGITAL 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 DIGITAL UNIX Programmer's Guide and the DIGITAL UNIX Using Programming Support Tools.
  • For performance information, see the DIGITAL UNIX System Tuning and Performance.
  • For an overview of DIGITAL UNIX documentation, see the DIGITAL UNIX Reader's Guide.
• Other layered product documentation
  If you are using a programming-related layered product package from DIGITAL, consult the appropriate documentation for the layered product package for use of that product.

Sending DIGITAL Your Comments on This Manual

DIGITAL welcomes your comments on this or any other DIGITAL Fortran 90 manual. You can send comments to us in the following ways:

• Internet electronic mail: fortran_docs@zko.mts.dec.com
• FAX: 603-884-0120 Attn: Languages Documentation, ZKO2-3/K35
• A letter sent to the following address:

  Digital Equipment Corporation Languages Documentation, ZKO2-3/K35 110 Spit Brook Road Nashua, NH 03062-2698 USA

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

Communicating with DIGITAL

If you have a customer support contract and have comments or questions about DIGITAL Fortran 90 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 DIGITAL Fortran product to the following Internet mail address: fortran@digital.com. Please note, however, that this address is for informational inquiries only. It is not a formal support channel.

DIGITAL World Wide Web Pages

If you have Internet access and a World Wide Web (WWW) viewer, you are invited to view the following:

• The DIGITAL Fortran home page, located at the following URL:

  http://www.digital.com/fortran/

• The Digital Equipment Corporation home page, located at:

  http://www.digital.com/

Conventions Used in This Document

This manual uses the conventions listed in Table 1.

Table 1 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 AXP	The terms to Alpha, Alpha systems, and AXP refer to the Alpha architecture or systems equipped with this 64-bit architecture.
DIGITAL UNIX DIGITAL UNIX systems	The terms DIGITAL UNIX and DIGITAL UNIX systems refer to the DIGITAL UNIX (formerly DEC OSF/1) operating system running on Alpha processor hardware.
Fortran	This term refers to language information that is common to the ANSI FORTRAN-77, ANSI/ISO Fortran 90, and DIGITAL Fortran 90.
Fortran 90	This term refers to language information that is common to ANSI/ISO Fortran 90 and DIGITAL Fortran 90.
DIGITAL Fortran 77 DEC Fortran	The term DIGITAL Fortran 77 (formerly DEC Fortran) refers to language information that is common to the FORTRAN-77 standard and any DIGITAL Fortran extensions.
DIGITAL Fortran 90 DEC Fortran 90	The term DIGITAL Fortran 90 (formerly DEC Fortran 90) refers to language information that is common to the Fortran 90 standard and any DIGITAL Fortran 90 extensions.
DIGITAL Fortran	DIGITAL Fortran 90 and DIGITAL Fortran 77 have been merged into the product known as DIGITAL Fortran. DIGITAL Fortran also refers to language features provided by both DIGITAL Fortran 77 and DIGITAL Fortran 90.
Parallel Software Environment	This term refers to an optional license and software that allows parallel execution of programs using High Performance Fortran (HPF) constructs.
HPF	This term refers to the High Performance Fortran Language.