Finding awesome developers in programming interviews

I can laugh about it now - was pretty gutted at the time.

I was going to write that your other possibility seemed like good advice too, but on consideration, it probably isn't, at least without caveats. In this particular example, it sounds like the problem was a lack of ready familiarity with printf. As weird as that function is, any decent programmer with a man page could work out how to do it in under an hour, I'd imagine. It would be insane not to hire someone you intended to do something like embedded development because of lack of printf experience.

On the other hand, take me as an example. I've got long professional experience writing platform independent software. But that experience is in the guts of the program; I've barely ever touched GUI stuff on any of those platforms. If you assumed my long experience with Windows, OS X, and Linux meant that I could program user interfaces on all three with ease and hired me for that reason, you'd find yourself in a world of hurt.

For highly specialized people, it's easy to forget trivial problems. They've just spent the last five or more years of their life honing their skills on a particular set of increasingly difficult problems. I'd be impressed if they could still scratch down a non-recursive fibonacci function off the top of their head. Most human beings cannot do that.

As an interviewer it's easy to forget that you're the only one who is interested in simple functions like reversing strings or shuffling cards. You do so at your own risk. The people walking through your door are expecting to talk about what they're good at. Unless the technology world has progressed at such breakneck speed because we've been mulling over how to best reverse strings for the past thirty years, then it's no surprise that such a narrow test is practically useless for all but junior first-time programmers.

He didn't explain, but the reasoning is that an embedded developer can work for years on projects that dont' have a screen, so there's nothing to print to.

I once found myself in a similar situation. After 2 years of working on an embedded C project (without a screen), I needed to print something. I found out to my horror that I didn't know how to do it - I'd only had experience with C++ before getting this job, so I only knew cout/cin. And even after 2 years of work on pretty hard embedded code in C, not having screen meant that printing had never come up.

Similarly, many embedded programmers who program in C++ have no experience with the Standard Library, Templates, and sometimes even the "new" keyword, since these are things you often don't use in embedded systems. You can get a false negative if you assume that anyone who doesn't know how to use the Standard Library after 6 years of C++ experience is obviously a bad programmer.