Software engineering, not computer science

Software Engineering, Not Computer Science

“A scientist builds in order to learn; an engineer learns in order to build.”
– Fred Brooks

When interviewing candidates for programming jobs, one of my favorite interview questions is, “How would you describe your approach to software development?” I give them examples such as carpenter, fire fighter, architect, artist, author, explorer, scientist, and archeologist, and I invite them to come up with their own answers. Some candidates try to second-guess what I want to hear; they usually tell me they see themselves as “scientists.” Hot-shot coders tell me they see themselves as commandos or swat-team members. My favorite answer came from a candidate who said, “During software design, I’m an architect. When I’m designing the user interface, I’m an artist. During construction, I’m a craftsman. And during unit testing, I’m one mean son of a bitch!”


like to pose this question because it gets at a fundamental issue in our field: What is the best way to think of software development? Is it science? Is it art? Is it craft? Is it something else entirely?

“Is” vs. “Should”
We have a long tradition in the software field of debating whether software development is art or science. Thirty ago, Donald Knuth began writing a seven-volume series, The Art of Computer Programming. The first three volumes stand at 2,200 pages, suggesting the full seven might amount to more than 5,000 pages. If that’s what the art of computer programming looks like, I’m not sure I ever want to see the science!

People who advocate programming as art point to the aesthetic aspects of software development and argue that science does not allow for such inspiration and creative freedom. People who advocate programming as science point to many programs’ high error rates and argue that such low reliability is intolerable – creative freedom be damned. Both these views are incomplete and both ask the wrong question. Software development is art. It is science. It is craft, archeology, fire fighting, sociology, and a host of other activities. It is amateurish in some quarters, professional in others. It is as many different things as there are different people programming. But the proper question is not “What is software development currently?” but rather “What should professional software development be?” In my opinion, the answer to that question is clear: Professional software development should be engineering. Is it? No. But should it be? Unquestionably, yes.

Engineering vs. Science
With only about 40 percent of software developers holding computer science degrees and practically none holding degrees in software engineering, we shouldn’t be surprised to find people confused about the difference between software engineering and computer science. The distinction between science and engineering in software is the same as the distinction in other fields.[1] Scientists learn what is true, how to test hypotheses, and how to extend knowledge in their field. Engineers learn what is true, what is useful, and how to apply well-understood knowledge to solve practical problems. Scientists must keep up to date with the latest research. Engineers must be familiar with knowledge that has already proven to be reliable and effective. If you are doing science, you can afford to be narrow and specialized. If you are doing engineering, you need a broad understanding of all the factors that affect the product you are designing.

Software engineering, not computer science