The real cost of interruption

I’m just back from reading Programmer Interrupted: The Real Cost of Interruption and Context Switching, an interesting short piece in which I learned about at least two new things.

First, The Parable of the Two Watchmakers, introduced by Nobel Prize winner Herbert Simon, describes the complex relationship between sub-systems and their larger wholes. In the context of the article, it helps explain, even for non-programmers, the cost of an interruption. It also hints at a possible mitigation technique:

There once were two watchmakers, named Hora and Tempus, who made very fine watches. The phones in their workshops rang frequently and new customers were constantly calling them. However, Hora prospered while Tempus became poorer and poorer. In the end, Tempus lost his shop. What was the reason behind this?

The watches consisted of about 1000 parts each. The watches that Tempus made were designed such that, when he had to put down a partly assembled watch, it immediately fell into pieces and had to be reassembled from the basic elements. Hora had designed his watches so that he could put together sub-assemblies of about ten components each, and each sub-assembly could be put down without falling apart. Ten of these sub-assemblies could be put together to make a larger sub-assembly, and ten of the larger sub-assemblies constituted the whole watch.

Second, larger computer screens help a programmer keep his mental model (and context) together. I’m still deciding on this one. Focusing on a single window or not having a lot of cruft around the screen helps solve complex code for me. But toss anything John Carmack at me, and I will abide.

The 640 x 480 resolution was the standard from 1990 to around 1996, but it was possible to get more screen real estate back then. There is a famous photo of John Carmack working on Quake using a 28-inch 1080p monitor in 1995.

Why did he choose 45 kg monitor for about $10k in 1995? The higher screen real estate allowed for more code to be visible at once, resulting in a more dense context. Productivity greatly increases when you have the ability to store and access more detailed context. It’s like having a larger desk to hold documents when studying for an exam or doing any task that requires the use of multiple sources of information from a common domain, such as solving puzzles.

The brilliant comic that opens the article is the perfect TL;DR for the Watchmakers parable.

This is why you shouldn't interrupt a programmer

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