The Four Programming Questions from My 1994 Microsoft Internship Interview

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The Four Programming Questions from My 1994 Microsoft Internship Interview<br>Interestingly enough, at least two of them were specifically about performance!

Casey Muratori<br>Aug 02, 2023

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There are no Performance-Aware Programming lessons this week because it is Summer Internship 1994 Week here on Computer, Enhance! This week will feature five posts about the programming questions I was asked when I interviewed for a Microsoft summer internship way, way back in 1994. Normally scheduled lessons will resume next week.

Long, long, long ago — I believe it was in 1994, but it could have been 1993 — I had to interview at Microsoft for a summer intern position. I interviewed with four separate people, and each one asked me a classic Microsoft interview “programming question”.<br>Of course, there wasn’t much of an internet back then, so I had no idea that was going to happen. I had no idea what a classic Microsoft programming question even was, or that they would be asking me them in the interviews.<br>What’s more, being young and inexperienced at the time, I had actually never had anyone ask me to solve a programming question on the spot before. It was a brand new experience for me, and although I would never recommend this style of question as an interview today, I can tell you that as a teenager it was a tremendous amount of fun.<br>It was so much fun, in fact, that I remember all four questions to this day.<br>This week, I’d like to share the four questions with you, talk about the answers that were “correct” at the time, and perhaps go a little further and ask what the “correct” answers might be today given the evolution of desktop computing. Each day this week, I’ll post an answer to one of the questions until we’ve completed all four.<br>For now, let’s look at the questions themselves…<br>Question #1: Rectangle Copy

I believe the idea behind the interview process was that the programming questions would get harder as you went through the day. So the first question was the easiest: write C code that copies a rectangle from one buffer to another.<br>I do not remember precisely which parameterization they gave me to do. Because this question was easy for me even at the time, my memory of it is less specific — but it was something like this:<br>void CopyRect(char *BufferA, int PitchA, char *BufferB, int PitchB,<br>int FromMinX, int FromMinY, int FromMaxX, int FromMaxY,<br>int ToMinX, int ToMinY)<br>/* Fill this in */<br>}In other words, given buffers A and B, a “From” rectangle in buffer A, and a “To” position in buffer B, write the code that copies the elements from A to B. Pixels were often only 8 bits at that time, so I believe the elements were 8-bits in this question.<br>As you can see, this is a pretty easy question, at least for anyone who knows C/C++. It might be a bit scarier for people who aren’t used to working with pointers, but in general, the idea of a rectangle copy is fairly straightforward. I was not asked to do anything specific with regards to the performance, either, so it was really just designed to see if I understood this kind of thing at all.<br>Question #2: String Copy

Weirdly, the second person who interviewed me asked a very similar question, but one that was seemingly easier than the first question. This was the only one that might be considered “out of sequence”, since questions 3 and 4 ramped up in difficulty quite a bit.<br>Question number two was a string copy. Generally speaking, if you can write a rectangle copy, you can write a string copy, but, I guess they had their reasons for asking this.<br>Specifically, the strings were ASCII-Z, which means one byte per element, null-terminated — something like this:<br>void CopyString(char *From, char *To)<br>/* Fill this in */<br>}This is a strange question for a number of reasons, not the least of which being the modifications that they asked me to make after I (successfully) wrote it out. Of the four interviews, in retrospect, this is the only one where I’m left wondering if maybe the interviewer didn’t really know their stuff that well… it’s hard to say, but, as I’ll describe in more detail when I answer this question, there were some things in this interview that, with the benefit of all the experience I have now, I look back on and scratch my head a little bit.<br>Question #3: Flood Fill Detection

The third question was by far the most interesting of the four, and quite a bit more difficult than the first two. It’s still not actually difficult, but given my relative inexperience with problems like it at the time, I was not able to solve this one on the spot. But it’s a fantastic little problem just the same!<br>The question comes from an implementation of a flood fill algorithm the interviewer had written for a Microsoft product. I forget which product, but I think it was some flavor of BASIC. It was for the graphics library of some language product like this,...