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T P E TG O
14T.I TLE AND SUBTITLE 5 FUNDING NUMBERS
Ada QUALITY AND STYLE: GUIDELINES FOR PROFESSIONAL
PROGRAMMERS
#E LE CT E l
n
SNOVI 1991
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SOFTWA PRODUCTIVTY CONSORTIUM, INC. CRSRF D EPCE VERSTO N THE
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13. ABSTRACT IMaximum 200 words)
THE SECOND EDITION HAS BEEN PRODUCED TO CORRECT, CLARIFY, AND ENHANCE VARIOUS TOPICS IN THE
ORIGINAL VERSION. INSTANTIATIONS HAVE BEEN INCLUDED WITHIN RELEVANT SECTIONS. WHILE THERE
HAVE BEEN CHANGES, ADDITIONS AND DELETIONS TO THE GUIDELINES, THE MAJOR CONCEPTUAL
CHANGES HAVE BEEN IN THE FOLLOWING AREAS: USE OF OTHERS CLAUSE IN CASE STATENEBTS, USE OF
WHILE LOOPS AND BLOCKS; EXCEPTION HANDLING, ANONYMOUS TASK TYPES, AND CONDITIONAL AND
TIMED ENTRY CALLS. THE SECTIONS ON COMMENTS AND THE CHAPTER ON REUSE HAVE BEEN EXPANDED.
THIS IS THE SUGGESTED Ada STYLE GUIDE FOR USE IN DoD PROGRAMS BY THE Ada JOINT PROGRAM
OFFICE.
14. SUBJECT TERMS 15. NUMBER OF PAGES
180
Ada STYLE GUIDE
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Ada Quality and Style:
Guidelines for Professional Programmers
SPC-91061-N
VERSION 02.00.02
1991
Software Productivity Consortium
SPC Building
2214 Rock Hill Road
Herndon, Virginia 22070-4005
Copyright © 1989, 1991 Software Productivity Consortium, Inc., Herndon, Virginia.
Permission to use, copy, modify and distribute this documentation for any purpose and
without fee is hereby granted, provided that the above copyright notice appears in all
copies and that both this copyright notice and this permission notice appear in supporting
documentation, and that the name Software Productivity Consortium, Inc. not be used in
advertising or publicity pertaining to distribution of the guidelines without specific,
written prior permission. Software Productivity Consortium, Inc. makes no
representations about the suitability of the guidelines described herein for any purpose. It
is provided "as is" without express or implied warranty.
Unlimited Distribution
Ada Quality and Style:
Guidelines for Professional Programmers
SPC-91 061 -N
VERSION 02.00.02
1991
6&6aFo
I TAL
-ULW La -1a
ID~st ipe 0 a1
91-14786
PREFACE
The second edition has been produced to correct, clarify, update and enhance various topics in the original
version. The book has undergone minor restructuring. While the chapters remain the same, some of the
sections have been rearranged for clarity. Also, instantiations have been included within relevant sections.
In some sections, there is an additional subsection on automation. While there have been changes,
additions and deletions to the guidelines, the major conceptual changes have been in the following areas:
use of the others clause in case statements, use of while loops and blocks, exception handling, anonymous
task types, and conditional and timed entry calls. The sections on comments and the chapter on reuse have
been expanded. Additionally, some examples have been enhanced.
We invite comments on this guidebook to continue enhancing its quality and usefulness. We will consider
suggestions for current guidelines as well as areas for future expansion. Examples that highlight particular
points are most helpful.
Please direct comments to:
Technology Transfer Division - AQS
Software Productivity Consortium
SPC Building
2214 Rock Hill Road
Herndon, Virginia 22070-4005
(703) 742-7211
Please fill out and mail the registration form at the back of this document to receive updates and other
information.
iv Ada QUALITY AND STYLE
v
AUTHORS AND ACKNOWLEDGEMENTS
The authors for the second edition are Kent Johnson, Elisa Simmons, and Fred Stluka. Contributors are
Alex Blakemore and Robert Hofkin. Reviewers include Alex Blakemore, Rick Conn, Tim Harrison, Dave
Nettles, and Doug Smith. Additional support has been provided by Vicki Clatterbuck, Leslie Hubbard, and
Debra Morgan.
The following people contributed to an instantiation of the first edition's guidelines: Rich Bechtold, Pete
Bloodgood, Shawna Gregory, Tim Powell, Dave Nettles, Kevin Schaan, Doug Smith and Perry Tsacoumis.
Special thanks are extended to Loral for providing feedback in the form of their Software Productivity
Laboratory Ada Standards.
The Consortium would also like to acknowledge those involved in the first edition. The authors were
Richard Drake, Samuel Gregory, Margaret Skalko, and Lyn Uzzle. Managing the project was Paul Cohen.
The contributors and reviewers were Mark Dowson, John Knight, Henry Ledgard, and Robert Mathis.
Word processing was performed by Debra Morgan.
Additional supporters included Bruce Barnes, Alex Blakemore, Terry Bollinger, Charles Brown, Neil
Burkhard, William Carlson, Susan Carroll, John Chludzinski, Vicki Clatterbuck, Robert Cohen, Elizabeth
Comer, Daniel Cooper, Jorge Diaz-Herrera, Tim Harrison, Robert Hofkin, Allan Jaworski, Edward Jones,
John A.N: Lee, Eric Marshall, Charles Mooney, John Moore, Karl Nyberg, Arthur Pyster, Samuel
Redwine, Jr., William Riddle, Lisa Smith, Fred Stluka, Kathy Velick, David Weiss, and Howard Yudkin.
vi Ada QUALITY AND STYLE
vii Ada QUALITY AND STYLE
CONTENTS
CHAPTER 1 Introduction ........................... 1
1.1 HOW TO USE THIS BOOK ..................................... 2
1.2 TO THE NEW Ada PROGRAMMER .............................. 3
1.3 TO THE EXPERIENCED Ada PROGRAMMER ..................... 3
1.4 TO THE SOFTWARE PROJECT MANAGER ....................... 3
CHAPTER 2 Source Code Presentation ................ 5
2.1 CODE FORMATTING .......................................... 5
2.2 SU M M A R Y .................................................. 15
CHAPTER 3 Readability .......................... 17
3.1 SP E L L IN G ................................................... 17
3.2 NAM ING CONVENTIONS ..................................... 19
3.3 COM M ENTS .............................................. . 24
3.4 U SIN G T Y PE S ............................................... 36
3.5 SU M M A RY .................................................. 37
CHAPTER 4 Program Structure ..................... 41
4.1 HIGH-LEVEL STRUCTURE .................................... 41
4.2 V ISIB IL IT Y .................................................. 45
4.3 EX C EPT IO N S ................................................ 50
4.4 SU M M A RY .................................................. 5 1
CHAPTER 5 Programming Practices ................ 55
5.1 OPTIONAL PARTS OF THE SYNTAX ........................... 55
5.2 PARA M ETER LISTS .......................................... 58
5 .3 T Y P E S .. .. .. .. .. .. .. .. . .. ... .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. . 6 2
5.4 DATA STRUCTURES ......................................... 64
5.5 EX PRESSIO N S ............................................ . 66
5.6 ST A T EM EN T S ............................................... 70
5.7 V ISIBILITY ..... .................................... . 77
5.8 USING EXCEPTIONS ......................................... 79
5.9 ERRONEOUS EXECUTION .................................... 81
5.10 SU M M A R Y .................................................. 85
vii
viii Ada QUALITY AND STYLE
CHAPTER 6 Concurrency ......................... 89
6.1 T A SK IN G ................................................... 89
6.2 COM M UNICATION ........................................... 94
6.3 TERM INATION ............................................. 100
6.4 SU M M A RY ................................................. 103
CHAPTER 7 Portability ............................ 105
7.1 FUNDAM ENTALS ........................................... 106
7.2 NUMERIC TYPES AND EXPRESSIONS ......................... 109
7.3 STORAGE CONTROL ........................................ 112
7.4 T A SK IN G .................................................. 113
7.5 EX C EPT IO N S ............................................... 115
7.6 REPRESENTATION CLAUSES AND IMPLEMENTATION-
DEPENDENT FEATURES ..................................... 116
7.7 IN PUT/O UTPUT ............................................. 119
7.8 SU M M A RY ................................................. 120
CHAPTER 8 Reusability .......................... 123
8.1 UNDERSTANDING AND CLARITY ............................ 124
8.2 RO BU STN ESS ............................................... 125
8.3 A DA PTA BILITY ............................................. 130
8.4 IN D EPEN D ENCE ............................................ 140
8.5 SU M M A RY ................................................. 142
CHAPTER 9 Instantiation ........................ 145
9.1 HORIZONTAL SPACING ..................................... 145
9.2 IN D EN TA T IO N .............................................. 146
9.3 MORE ON ALIGNM ENT ..................................... 148
9.4 PA G IN A T IO N ............................................... 148
9.5 SOURCE CODE LINE LENGTH ............................... 148
9.6 N U M B E RS .................................................. 149
9.7 CA PITA LIZATIO N .......................................... 149
9.8 FILE H EA D ERS ............................................. 149
9.9 PROGRAM UNIT SPECIFICATION HEADER .................... 149
9.10 PROGRAM UNIT BODY HEADER ............................. 150
9.11 NAM ED ASSOCIATION ...................................... 150
9.12 ORDER OF PARAMETER DECLARATIONS ..................... 151
9 .13 N E ST IN G ................................................... 15 1
9.14 GLOBAL ASSUM PTIONS ..................................... 151
CHAPTER 10 Complete Example .................. 153
APPENDIX A - Map from Ada Language Reference
Manual to Guidelines .............. 163
REFERENCES ................................. 169
BIBLIOGRAPHY ................................. 172
INDEX ......................................... 175
viii
