Few books on software project management have been as influential and timeless asThe Mythical Man-Month. With a blend of software engineering facts and thought-provoking opinions, Fred Brooks offers insight for anyone managing complex projects. These essays draw from his experience as project manager for the IBM System/360 computer family and then for OS/360, its massive software system. Now, 20 years after the initial publication of his book, Brooks has revisited his original ideas and added new thoughts and advice, both for readers already familiar with his work and for readers discovering it for the first time.

The added chapters contain (1) a crisp condensation of all the propositions asserted in the original book, including Brooks' central argument in The Mythical Man-Month: that large programming projects suffer management problems different from small ones due to the division of labor; that the conceptual integrity of the product is therefore critical; and that it is difficult but possible to achieve this unity; (2) Brooks' view of these propositions a generation later; (3) a reprint of his classic 1986 paper "No Silver Bullet"; and (4) today's thoughts on the 1986 assertion, "There will be no silver bullet within ten years."

Frederick P. Brooks, Jr., was born in 1931 in Durham, NC. He received an A.B. summa cum laude in physics from Duke and a Ph.D. in computer science from Harvard, under Howard Aiken, the inventor of the early Harvard computers.

At Chapel Hill, Dr. Brooks founded the Department of Computer Science and chaired it from 1964 through 1984. He has served on the National Science Board and the Defense Science Board. His current teaching and research is in computer architecture, molecular graphics, and virtual environments.

He joined IBM, working in Poughkeepsie and Yorktown, NY, 1956-1965. He is best known as the "father of the IBM System/360", having served as project manager for its development and later as manager of the Operating System/360 software project during its design phase. For this work he, Bob Evans, and Erick Block were awarded and received a National Medal of Technology in 1985.

Dr. Brooks and Dura Sweeney in 1957 patented a Stretch interrupt system for the IBM Stretch computer that introduced most features of today's interrupt systems. He coined the term computer architecture . His System/360 team first achieved strict compatibility, upward and downward, in a computer family. His early concern for word processing led to his selection of the 8-bit byte and the lowercase alphabet for the System/360, engineering of many new 8-bit input/output devices, and providing a character-string datatype in PL/I.

In 1964 he founded the Computer Science Department at the University of North Carolina at Chapel Hill and chaired it for 20 years. Currently, he is Kenan Professor of Computer Science. His principal research is in real-time, three-dimensional, computer graphics-"virtual reality." His research has helped biochemists solve the structure of complex molecules and enabled architects to "walk through" buildings still being designed. He is pioneering the use of force display to supplement visual graphics.

Brooks distilled the successes and failures of the development of Operating System/360 in The Mythical Man-Month: Essays in Software Engineering, (1975). He further examined software engineering in his well-known 1986 paper, "No Silver Bullet." He is just completing a two-volume research monograph, Computer Architecture, with Professor Gerrit Blaauw. Now, 20 years after the initial publication of his book, Brooks has revisited his original ideas and added new thoughts and advice within The Mythical Man-Month, Anniversary Edition.

Brooks has served on the National Science Board and the Defense Science Board. He is a member of the National Academy of Engineering and the American Academy of Arts and Sciences. He has received the the IEEE John von Neumann Medal, the IEEE Computer Society's McDowell and Computer Pioneer Awards, the ACM Allen Newell and Distinguished Service Awards, the AFIPS Harry Goode Award, and an honorary Doctor of Technical Science from ETH-Zürich.

Peter Gordon, now a Publishing Partner at Addison-Wesley, has been working with me patiently and helpfully since 1980. He proposed that we prepare an Anniversary Edition. We decided not to revise the original, but to reprint it untouched (except for trivial corrections) and to augment it with more current thoughts.

Chapter 16 reprints "No Silver Bullet: Essence and Accidents of Software Engineering," a 1986 IFIPS paper that grew out of my experience chairing a Defense Science Board study on military software. My co-authors of that study, and our executive secretary, Robert L. Patrick, were invaluable in bringing me back into touch with real-world large software projects. The paper was reprinted in 1987 in the IEEE Computer magazine, which gave it wide circulation.

"No Silver Bullet" proved provocative. It predicted that a decade would not see any programming technique which would by itself bring an order-of-magnitude improvement in software productivity. The decade has a year to run; my prediction seems safe. "NSB" has stimulated more and more spirited discussion in the literature than has The Mythical Man-Month. Chapter 17, therefore, comments on some of the published critique and updates the opinions set forth in 1986.

In preparing my retrospective and update of The Mythical Man-Month, I was struck by how few of the propositions asserted in it have been critiqued, proven, or disproven by ongoing software engineering research and experience. It proved useful to me now to catalog those propositions in raw form, stripped of supporting arguments and data. In hopes that these bald statements will invite arguments and facts to prove, disprove, update, or refine those propositions, I have included this outline as Chapter 18.

Chapter 19 is the updating essay itself. The reader should be warned that the new opinions are not nearly so well informed by experience in the trenches as the original book was. I have been at work in a university, not industry, and on small-scale projects, not large ones. Since 1986, I have only taught software engineering, not done research in it at all. My research has rather been on virtual reality and its applications.

In preparing this retrospective, I have sought the current views of friends who are indeed at work in software engineering. For a wonderful willingness to share views, to comment thoughtfully on drafts, and to re-educate me, I am indebted to Barry Boehm, Ken Brooks, Dick Case, James Coggins, Tom DeMarco, Jim McCarthy, David Parnas, Earl Wheeler, and Edward Yourdon. Fay Ward has superbly handled the technical production of the new chapters.

I thank Gordon Bell, Bruce Buchanan, Rick Hayes-Roth, my colleagues on the Defense Science Board Task Force on Military Software, and, most especially, David Parnas for their insights and stimulating ideas for, and Rebekah Bierly for technical production of, the paper printed here as Chapter 16. Analyzing the software problem into the categories of essence and accident was inspired by Nancy Greenwood Brooks, who used such analysis in a paper on Suzuki violin pedagogy.

Addison-Wesley's house custom did not permit me to acknowledge in the 1975 Preface the key roles played by their staff. Two persons' contributions should be especially cited: Norman Stanton, then Executive Editor, and Herbert Boes, then Art Director. Boes developed the elegant style, which one reviewer especially cited: "wide margins, [and] imaginative use of typeface and layout." More important, he also made the crucial recommendation that every chapter have an opening picture. (I had only the Tar Pit and Rheims Cathedral at the time.) Finding the pictures occasioned an extra year's work for me, but I am eternally grateful for the counsel.

Deo soli gloria or Soli Deo Gloria -- To God alone be the glory. Chapel Hill, N.C., F.