The Mythical Man-Month

Frederic P. Brooks

Why is programming Fun?

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 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 the principles built in from the beginning. The programmed computer has all the fasciantion 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 always new, and its solver learns something: sometimes practical, sometimes theoretical, and sometmes 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.

Yet the program construct, unlike the poet's words, is real in the sense that in moves and works, producing visible outputs seperate 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 the 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.

Self-Discipline: The Second System Effect

An architect's first work is apt to be spare and clean. He knows he dosen't know what he's doing, so he does it carefully and with great restraint.

As he designs his first work, frill after frill, embellishment after embillishment occour to him. These get stored away to be used "next time." Sooner or later the first system is finished, with firm confidence and a demonstrated mastery of that class of systems, is ready to build a second system.

This second is the most dangerous system a man ever designs. ...The general tendecy is to over-design the second system, using all the ideas and frills that were cautiously sidetracked on the first one. For example, consider the IMB 709 architecture, later embodied in the 7090. this is an upgrade, a second system for the very successful and clean 704. The operation set is so rich and profuse that only about half of it was regularly used.

The second-system effect has another manifestation somewhat different from pure functional embellishment. that is a tendency to refine techniques whose very existence has been made obsolete by changes in basic system assumptions. OS/360 has many examples of this.

Consider the linkage editor, designed to load separately-compiled programs and resolve their cross references. Beyond this basic function it also handles program overlays. It is one of the finest overlay facilities ever built. It allows overlay structuring to be done externally, at linkage time, without being designed into the source code. It allows the overlay structure to be changes from run to run without recompilation. It furnished a rich variety of useful options and facilities. In a sense it is the culmination of years of development of static overlay technique.

Yet it is also the last and finest of the dinosaurs, for it belongs to a system in which multiprogramming is the normal mode and dynamic core allocation the basic assumption. this is in direct conflict with the notion of using static overlays. how much better the system would work if if the efforts devoted to overlay management had been spent on making the dynamic core allocation and the dynamic cross-referencing facilities really fast!