Why developers hate being interrupted

Heads up! This post was written in 2015, so it may contain information that is no longer accurate. I keep posts like this around for historical purposes and to prevent link rot, so please keep this in mind as you're reading.

— Cory

I stumbled across a post today (that unfortunately no longer exists) and I was almost convinced that I had written it myself. Many of the points in it hit home, so I hope it helps people better understand how developers think and what they go through when interruptions arise.

One point talks about how much headwork programming requires:

A huge amount of what a developer is doing is in their head. As we write code we need to keep a mental model of how parts of the application that have already been written and are yet to be written interact with the part that we are writing at that moment. We need to have a solid picture of exactly how the code is working as a whole and maintain that picture. It’s not easy, it requires a lot of concentration and has to remain in place while we think of creative and efficient ways to solve the problem at hand.

Another explains why developers are actually the most productive when they seem unproductive:

Developers can appear very unproductive at times, sitting staring at the screen with our headphones on and very little in the way of keyboard clackety-tap. This however is when we are doing our thinking, when we are building up, adding to and rearranging the mental model of how our code will work. This is the biggest and hardest part of development.

It's so true. Breaking a developer's concentration can be devastating to their productivity.