This is a very commonly asked question – asked in interviews with Microsoft, Google, and many other companies.

Although this question really has nothing to do with any programming job, it gives an interviewer the opportunity to see how a potential candidate would structure their thinking when approaching a problem.

Keep in mind that getting the right answer to this question is not as important as showing the interviewer that your thinking is structured logically. When approaching a question like this, it helps to get to a more specific question and then try to answer that question instead of the one originally asked. It’s like someone were to give you a 3 week project, consisting of many different tasks – you basically divide the project into tasks to get the whole thing completed. Similarly, you want to "break" the question down into more manageable "pieces", because you can’t really answer it the way it is.