One view of object-oriented programming is that it is a discipline that enforces modularity and clean interfaces. A second view emphasizes encapsulation, the fact that one cannot see, much less design, the inner structure of the pieces. Another view emphasizes inheritance, with its concomitant hierarchical structure of classes, with virtual functions. Yet another view emphasizes strong abstract data-typing, with its assurance that a particular data-type will be manipulated only by operations proper to it.
Now any of these disciplines can be had without taking the whole Smalltalk or C++ package—many of them predated object-oriented technology. The attractiveness of object-oriented approach is that of a multivitamin pill: in one fell swoop (that is, programmer retraining), one gets them all. It is a very promising concept.
Why has object-oriented technique grown slowly? In the nine years since “NSB,” the expectancy has steadily grown. Why has growth been slow? Theories abound. James Coggins, author for four years of the column, “The Best of comp.lang.c++ ” in The C++ Report, offers this explanation:
The problem is that programmers in O-O have been experimenting in incestuous applications and aiming low in abstraction, instead of high. For example, they have been building classes such as linked-list or set instead of classes such as user-interface or radiation beam or finite-element model. Unfortunately the self-same strong type checking in C++ that helps programmers to avoid errors also makes it hard to build big things out of little ones.
He goes back to the basic software problem, and argues that one way to address unmet software needs is to increase the size of the intelligent workforce by enabling and coopting our clients. This argues for top-down design:
we design large-grained classes that address concepts our clients are already working with, they can understand and question the design as it grows, and they can cooperate in the design of test cases. My ophthalmology collaborators don’t care about stacks; they do care about Legendre polynomial shape descriptions of corneas. Small encapsulations yield small benefits.
David Parnas, whose paper was one of the origins of object-oriented concepts, sees the matter differently. He writes me:
The answer is simple. It is because [O-O] has been tied to a variety of complex languages. Instead of teaching people that O-O is a type of design, and giving them design principles, people have taught that O-O is the use of a particular tool. We can write good or bad programs with any tool. Unless we teach people how to design, the languages matter very little. The result is that people do bad designs with these languages and get very little value from them. If the value is small, it won’t catch on.
-Fred Brooks, The Mythical Man-Month, pg. 220
Posts Tagged fred brooks
The Joys of the Craft
Why is programming fun? What delights may its practitioner expect as his reward?
First is the sheer joy of making things. As the child delights in his mud pie, so the adult enjoys building things, especially things of his own design. I think this delight must be an image of God’s delight in making things, a delight shown in the distinctness and newness of each leaf and each snowflake.
Second is 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. In this respect the programming system is not essentially different from the child’s first clay pencil holder “for Daddy’s office.”
Third is 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 programmed computer has all the fascination of the pinball machine or the jukebox mechanism, carried to the ultimate.
Fourth is 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.
Finally, there is the delight of working in such a tractable medium. The programmer, like the poet, works only slightly removed from pure thought-stuff. He builds his 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. (As we shall see later, this very tractability has its own problems.)
Yet the program construct, unlike the poet’s words, 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.
-Fred Brooks, The Mythical Man-Month, pg. 8-9