IN 1937 THE MATHEMATI cian Alan Turing laid the foundation for modern computer science by introducing the concept of a Turing machine. Such a device could do four things: make a mark on a strip of paper, erase a mark, and move the paper forward or backward. In theory, a digital computer program of any complexity can be broken down into equivalents of these four steps.

The concept has applications outside the world of computer science. The academic profession, for example, sometimes works like a gigantic Turing machine, with half its members penciling in boundaries between disciplines or ideas- science and technology, invention and discovery, high and low culture —while the other half just as busily erases them and both groups tug the debate in alternating directions. To outsiders this process of distinguishing between one field or area of inquiry and another may seem as important as deciding whether Certs is a candy mint or a breath mint.

Two museum exhibits in New York City this spring confronted the same type of border dispute in disciplines related to technology. At the American Craft Museum, “Defining Craft” (which recently closed) used artifacts and quotations to take a shot at resolving the lexicographic problem that formed the exhibit’s title. In the end, to no one’s surprise, craft turned out to mean different things to different people.

The objects on display were impressively diverse: glassware, textiles, ceramics, cutlery, furniture, and many others. In these surroundings, so redolent of the forge and the workbench, it was disconcerting to come across the artist Judy Chicago’s pronouncement that “the use of the terms art and craft has been a pretext for discrimination between gender activities. If men did it, it was art. If women did it, it was craft .” Several other participants in the show revealed the same craving to feel scorned, complaining that their work is not considered worthy of display at art museums. Considering what does tend to be displayed at art museums these days, it’s probably just as well.

Perhaps the most telling comment in the exhibit was written in 1882 by William Morris, the English designer and poet: “Never forget the material you are working with. … the special limitations of the material should be a pleasure to you, not a hindrance.” With this bit of advice Morris neatly sums up what crafts are about. No modern airplane designer (except one serving the antiquarian market) would build a plane of wood if titanium was more efficient. Nor would a designer of sewage systems honor his forebears in the profession by using hollowed-out logs as pipes. To a craftsman, by contrast, the value of an object often has little or nothing to do with how well it works. Some items in the show were purely decorative, without even a gesture toward functionality, while others took the form of a bowl or a chair but will never hold salad or be sat on.

Farther uptown, at the Cooper-Hewitt National Design Museum, the first National Design Triennial is on view through August 6. The idea behind this exhibit is to create for modern design the same buzz that the Whitney Museum’s Biennial creates for modern art, though one hopes without that institution’s ever-more-futile attempts to shock New York’s dwindling bourgeoisie. To make sense of a collection of items united only by the vague notion of “design,” the Cooper-Hewitt’s curators have organized the exhibit by concepts: “fluid,” “physical,” “minimal,” “reclaimed,” and so on.

Hard-core design fans will find these categories rewarding. The rest of us will simply be dazzled by the objects on display, from the practical (a bright yellow-and-red voltmeter by Fluke Corporation of Everett, Washington, that looks like something a toddler would play with in the bathtub) to the monumental (Jim Seay’s Batman and Robin roller coaster for a New Jersey amusement park) to the virtual (a series of buildings, installations, and devices that exist only as computer renderings).

The most whimsical item in the show is a Pink Pantherpink bicycle designed by Robert Egger of Morgan Hill, California, that has flower-power decorations and a foldout compartment with a martini shaker and glasses. According to the label, the bicycle’s “retro flavor draws from the Austin Powers movies.” We all know Karl Marx’s epigram that history repeats itself, “the first time as tragedy, the second time as farce.” But what if the first time around was already a farce? The current wave of campy 1960s nostalgia definitively answers that question.

Where, then, shall we draw the lines between craft, design, and engineering? At a certain level of abstraction, the goals of all three are the same: to produce something useful and aesthetically pleasing. In real life, however, it is not always possible to achieve both these things, and when compromises must be made, the boundaries become clear. Craft, above all else, must be authentic. For something to qualify as a craft object, there must be an element of traditional practice in its creation, or at the very least it must be inspired by or based on tradition. (It also must actually exist; computer renderings are not craft.) This is why craft objects tend to be unique or produced in small lots.

For design, the inescapable criterion is appearance: A well-designed object must look good. The method of its creation is irrelevant, which is why a talented industrial designer can go from cars to buildings to drink dispensers to book jackets, while craft workers tend to specialize in one thing. And while function should ideally be taken into account, it is often decidedly secondary, as anyone who has sat in a modernist armchair can attest. Indeed, some of the most familiar triumphs of industrial design, such as Raymond Loewy’s locomotive bodies, are nothing more than decorations for the technology underneath.

As for engineering, the sine qua non is simple: It has to work. While a well-engineered bridge or automobile will usually be aesthetically pleasing, poorly engineered examples can look just as good. If they collapse or fail to start, however, no amount of art theory will remedy the situation. This is what sets engineering apart from the allied disciplines mentioned above—and why good engineering is best experienced not in a museum but in the ordinary course of our daily lives.

At a recent family gathering the three-year-old nephew of one of our editors spent hours on end running around the house re-enacting episodes of “Blue’s Clues,” a popular children’s television series that stars an animated dog. The adults bore it with resignation, and after a day or so their patience was rewarded when the youngster abruptly switched to “Sesame Street.” The change was a great relief, if only on the alternative-irritation theory, until somebody was unwise enough to say out loud, “You know, it’s been almost an hour since he mentioned ‘Blue’s Clues.’” On hearing this, the boy’s ears perked up, and he instantly segued back to the dreaded azure canine. Realizing what had happened, the grownup who had been so fatally indiscreet buried his head in his hands as the others gritted their teeth and plotted revenge.

It is with similar trepidation that this column ventures to mention the word century . Surely the greatest cause for celebration on January 1 was the knowledge that not for another 99 years would we have to suffer through the futile and interminable debate over when a century begins and ends. Unfortunately, though, some partisans still lie in wait for any pretext to renew the argument. Yet despite this peril, the arrival of 2000 has not stopped Americans from compiling best-of-the-century lists, and at least one such list is worth braving the fanatics to discuss: a well-considered compilation of Greatest Engineering Achievements of the Twentieth Century, released earlier this year by the National Academy of Engineering (NAE). Twenty-seven engineering societies participated in the selection process, and the allstar committee that decided the final ranking included the astronaut Neil Armstrong, the engineer and Invention & Technology contributor Henry Petroski, the laser inventor and Nobel laureate Charles H. Townes, the presidents of Virginia Tech and MIT, and two dozen other luminaries.

In a sense, assessing one technology against another is a little like deciding whether your heart or your lungs are more important. Rankings of this sort can also recall the comment made in 1945 by Harold Ross, the long-time editor of The New Yorker : “I regard such discussions… as in a class with the debates I used to hear as a lad in Salt Lake City as to whether Fannie Brown or Helen Blazes was the best in the five-dollar bracket.” Still, weighing the changes brought about by different technologies can yield valuable insights on how the process of change occurs, as well as on the effects technology has had on all our lives.

The items on the NAE’s final list are broad categories rather than specific inventions or people. The complete list can be viewed at www.greatachievements.org, but to end the suspense, we will reveal that Electrification tops the list. Computers are way down at number 8, although the Internet has its own entry at number 13. At 14 is the catchall category of Imaging, which brings together photography, microscopy, medical imaging, radar, sonar, and various other technologies. By contrast, Household Appliances, at number 15, discusses toasters extensively but excludes the Ziploc plastic bag, surely the century’s most valuable aid to homemakers. But apart from such quibbles (which can be made about any ranking), the NAE list is judicious and thought-provoking. Best of all, it is sure to provoke debates much more stimulating than the profoundly tiresome century question.