Chapter 1: The Tar Pit

A ship on the beach is a lighthouse to the sea.


Over the years, all kind of animals have sunk in tar pits despite their efforts to scape.

Large-system programming has over the past decade been such a tar pit, and many great and powerful beasts have thrashed violently in it. Most have emerged with running systems—few have met goals, schedules, and budgets. Large and small, massive or wiry, team after team has become entangled in the tar. No one thing seems to cause the difficulty—any particular paw can be pulled away. But the accumulation of simultaneous and interacting factors brings slower and slower motion. Everyone seems to have been surprised by the stickiness of the problem, and it is hard to discern the nature of it. But we must try to understand it if we are to solve it.

Programming System Products

Obsession with transition from garage programming to real programming system product

We start with a program, THAT is the thing commonly produced in garages, and what is used by the individual programmer for doing productivity estimations

There are two ways a program can be converted into a more useful, but more costly, object:


  • A programming product can be run, tested, repaired, and extended by anybody. It is usable in many operating environments, for many sets of data.
  • To become a generally usable programming product, must be written in a generalized fashion.
  • The range and form of inputs must be generalized as much as the basic algorithm will reasonably allow.
  • Then the program must be thoroughly tested, so that it can be depended upon. (A substantial bank of test cases, exploring the input range and probing its boundaries, must be prepared, run, and recorded)
  • Finally, promotion of a program to a programming product requires its thorough documentation, so that anyone may use it, fix it, and extend it.
  • I estimate that a programming product costs at least three times as much as a debugged program with the same function.


  • A programming system is a collection of interacting programs, coordinated in function and disciplined in format (the assemblage constitutes an entire facility for large tasks.)
  • To become a programming system component, a program must be written so that every input and output conforms in syntax and semantics with precisely defined interfaces.
  • The program must also be designed so that it uses only a prescribed budget of resources—memory space, input-output devices, computer time.
  • Finally, the program must be tested with other system components, in all expected combinations. This testing must be extensive, for the number of cases grows combinatorially. It is time-consuming, for subtle bugs arise from unexpected interactions of debugged components.
  • A programming system component costs at least three times as much as a stand-alone program of the same function.


  • This differs from the simple program in all of the above ways.
  • It costs nine times as much. But it is the truly useful object, the intended product of most system programming efforts.


The Joys of the Craft

Why is programming fun? What delights may its practitioner expect as his reward?

  • The sheer joy of making things.
  • The pleasure of making things that are useful to other people. Deep within, we want others to use our work and to find it helpful.
  • The fascination of fashioning complex puzzle-like objects of interlocking moving parts and watching them work in subtle cycles, playing out the consequences of principles built in from the beginning.
  • The joy of always learning, which springs from the nonrepeating nature of the task. In one way or another the problem is ever new, and its solver learns something: sometimes practical, sometimes theoretical, and sometimes both.
  • The delight of working in such a tractable medium. Almost pure thought-stuff. Building castles in the air, from air, creating by exertion of the imagination.

Few media of creation are so flexible, so easy to polish and rework, so readily capable of realizing grand conceptual structures.

Yet the program construct is real in the sense that it moves and works, producing visible outputs separate from the construct itself. It prints results, draws pictures, produces sounds, moves arms. The magic of myth and legend has come true in our time. One types the correct incantation on a keyboard, and a display screen comes to life, showing things that never were nor could be.

Programming then is fun because it gratifies creative longings built deep within us and delights sensibilities we have in common with all men.

The Woes of the Craft

  • Not all is delight, however, and knowing the inherent woes makes it easier to bear them when they appear.
  • One must perform perfectly. Human beings are not accustomed to being perfect, and few areas of human activity demand it. Adjusting to the requirement for perfection is the most difficult part of learning to program.
  • Other people set one’s objectives, provide one’s resources, and furnish one’s information. One rarely controls the circumstances of his work, or even its goal. In management terms, one’s authority is not sufficient for his responsibility.
  • The dependence upon others has a particular case that is especially painful for the system programmer. He depends upon other people’s programs (often maldesigned, poorly implemented, incompletely delivered (no source code or test cases), and poorly documented). Forcing to  spend hours studying and fixing things that in an ideal world would be complete, available, and usable.
  • Designing grand concepts is fun; finding nitty little bugs is just work. With any creative activity come The Woes of the Craft dreary hours of tedious, painstaking labour.
  • Debugging has a linear convergence, so testing drags on and on, the last difficult bugs taking more time to find than the first.
  • The product over which one has laboured so long appears to be obsolete upon (or before) completion. The technological base on which one builds is always advancing. As soon as one freezes a design, it becomes obsolete in terms of its concepts. But implementation of real products demands phasing and quantizing. The obsolescence of an implementation must be measured against other existing implementations, not against unrealized concepts.

The challenge and the mission are to find real solutions to
real problems on actual schedules with available resources.

This then is programming, both a tar pit in which many efforts have floundered and a creative activity with joys and woes all its own. For many, the joys far outweigh the woes, and for them the remainder of this book will attempt to lay some boardwalks across the tar.


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