Computer Engineer vs. Computer Scientist

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Computer Engineer vs. Computer Scientist

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Which one are you? I am an engineer. But maybe we should first define the differences between the two. Engineer cares about how the system is put together whereas CS cares about how it works. Do you care about the technology or the algorithm?

The Interview

Since I am on engineer, these are the kind of questions I ask in an interview:

  • Imagine you are an evil developer, how do you make code hard to test?
  • How would you store a math expression tree, such that you would have an evaluate() method and a toString() method which would print the tree in an infix notation placing the parenthesis only when necessary.

On the other hand a CS asks these “algorithmic” questions:

  • Write a merge sort method which merges ‘n’ files into one.
  • Write a method to reverse a string in place.

The solution to engineer’s question is a set of classes interacting to define a system. Whereas a solution to a CS question is a single method doing something complex. Now, I don’t know about you but when was the last time when your application consisted of a single method. When was the last time when your system broke down because someone did not know how to write one of these algorithmic methods? When was the last time when your system broke down because the interaction between classes has gone too complex? I believe that most people are asking the wrong questions in the interview.


Now there is a time and place when an algorithm is exactly what the doctor ordered. Video/voice codecs, image compression, revision control, database optimization, and so on. But notice that all of these are nothing without some “application” around it. Video codec is nothing without YouTube around it, and DB engine is nothing without countless utilities, and database drivers which go with it. Chances are, when you are building an application, you will fail because  your class interaction will go out of hand, not because you did not know how to solve some algorithmic problem. Libraries have already been written for the most (80%) of the algorithmic problems out there. So why do you insist that an interview candidate knows how to sort integers. Is that what he/she will be doing all day long? While building your web application?

Engineer vs CS

The thing is you need both, and preferably in one person. It is also true that no one is 100% engineer or 100% CS, there is a blend in all of us. Algorithms require raw brain power, whereas engineering requires prior knowledge (best practices) which you cannot get by thinking about the problem harder. You can only get “engineering” knowledge by learning from others. I have seen too many people focusing too much on brain power alone. We hire young kids and we let them loose on a code-base, and than we wonder why we can’t change anything because everything is tightly coupled. Hint, it is not because they are stupid.

The Reality

The truth is in the ten years or so I have been out of school I have been fighting bad code every step of the way. I can’t remember when was the last time I had to solve an algorithmic problem. The most complex/algorithmic intensive code I have written was Testability Explorer, which is a byte code analysis engine which tries to determine how testable your code is. I have written it in my free time, and the thing which enabled me to write such a complex “algorithm” were unit tests, and lots of them! I had to rely on “best-engineering-practices” to build something which is “algorithm intensive”. In other words it is my engineering background not my CS which made it possible. I think CS, is required but insufficient.

Going Forward

I would love for the industry to reflect on itself and realize that its problems is not lack of CS majors, or a the lack of bright people, but a lack of good old fashion engineers, thetn maybe we may start asking a lot more questions, to which the answer is not a single method, but a collection of classes interacting together. It took a handful of scientist to come up with an atom bomb, but it took countless of engineers to work out everything else, and software is no different. You need a handful of CS, and an army of engineers.

From http://misko.hevery.com


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