COMPUTER APPLICATIONS

WINDOWS IN BLACK BOXES

PETER KENNEDY*

In a recent issue of this journal, Wykoff [1989] complains that student use of canned computer programs ("black boxes") is a non-intellectual ac- tivity, inhibiting student learning and fostering sloppy habits. He suggests having students write their own programs in an on-line, interactive environ- ment, and argues, convincingly, that this approach has pedagogical, scientific and intellectual virtues. One cost of achieving these benefits is that students must learn a programming language; Wykoff advocates APL because it is compact, flexible and well-suited to economic and statistical analysis. A second cost, not noted by Wykoff, is that students will not become familiar with how a popular computer package works and what it can (and cannot) do.

The purpose of this note is to bring to readers' attention that major com- puter packages, such as SAS, TSP and SHAZAM, have for several years now had programming languages built into them. Because these languages allow all the Wykoff objectives to be captured from within the canned packages, I characterize them as providing windows for black boxes. These languages, when compared to APL, are as compact, as flexible, as well-suited to statis- tical analysis, as easy to learn, and as powerful (they also use the array as the unit of operation). Furthermore, because these languages permit students to interface directly with the black box and exploit its contents for a variety of purposes, they dominate APL for use in econometrics courses. To be explicit, consider the following advantages.

a) By using a language in a computer package students will be forced to become familiar with that computer package, eliminating one of the two major costs of the Wykoff suggestion.

b) Since it is likely that students eventually will have to use a package, the cost of an APL text can be saved.

c) Wykoff stresses that a major benefit of having students learn program- ming is that they will be able to program new tests or techniques that are not available in a package. In contrast to APL manuals, computer package manuals contain explicit examples of how estimation techniques not avail- able on that package can be programmed. See, for example, pp. 207-32 in White, Haun and Horsman [1987].

* Simon Fraser University

638 Economic Inquiry VOI. XXVIII, July 1990, 638-639

KENNEDY: WINDOWS IN BLACK BOXES 639

d) Programming an estimation technique often requires use of subroutines which are not of inherent interest, because they are exercises in mathematics or numerical analysis. If programming is done from within a package, such subroutines can be called from the package, allowing students to focus on those dimensions of the programming problem that will enhance their un- derstanding of the econometric technique in question.

e) A common exercise for students is to have them obtain a result through programming and then show that it is identical to the result given by a computer package. This comparison can be done more efficiently if the stu- dent is operating from within that package.

f ) After graduation, empirical work will likely be done through a com- puter package, so familiarity with how programming can be exploited within such a package will be of value.

g) APL requires more computer time than do languages in computer pack- ages. This handicaps Monte Carlo work, as one of my students discovered to his great dismay.

h) If students are doing their computer work on microcomputers, as is more and more the case, two pieces of software would be required if both APL and the computer package were to be used.

acters, so students would have to learn a new keyboard. i) As Wykoff's examples illustrate, APL uses many non-standard char-

The comments above assume that the programming is used in the context of an econometrics course, as Wykoff's examples suggest. Wykoff notes, however, that his APL programming approach can be useful in non-econo- metrics courses, such as principles courses. His case is stronger here. The programming languages in the computer packages are designed specifically for statistical work, so that although they could perform the model-building tasks that Wykoff has in mind for principles students, they would not do it as efficiently as APL. In the context of econometrics courses, however, it seems clear that the Wykoff suggestion is best realized through use of a programming language available in a computer package.

REFERENCES

White, Kenneth I., Haun, Shirley A. and Nancy G. Horsman. SHAZAM User's Reference Munuul.

Wykoff, Frank C. "Economics: On Line and Interactive." Economic Inquiry, July 1989, 547-54. Vancouver: University of British Colombia, 1987.