Five Worlds – Joel on Software

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Something important is almost never mentioned in all the literature about programming and software development, and as a result we sometimes misunderstand each other.

You’re a software developer. Me too. But we may not have the same goals and requirements. In fact there are several different worlds of software development, and different rules apply to different worlds.

You read a book about UML modeling, and nowhere does it say that it doesn’t make sense for programming device drivers. Or you read an article saying that "the 20MB runtime [required for .NET] is a NON issue" and it doesn’t mention the obvious: if you’re trying to write code for a 32KB ROM on a pager it very much is an issue!

I think there are five worlds here, sometimes intersecting, often not. The five are:

Shrinkwrap<br>Internal<br>Embedded<br>Games<br>Throwaway

When you read the latest book about Extreme Programming, or one of Steve McConnell’s excellent books, or Joel on Software, or Software Development magazine, you see a lot of claims about how to do software development, but you hardly ever see any mention of what kind of development they’re talking about, which is unfortunate, because sometimes you need to do things differently in different worlds.

Let’s go over the categories briefly.

Shrinkwrap is software that needs to be used "in the wild" by a large number of people. It may be actually wrapped in cellophane and sold at CompUSA, or it may be downloaded over the Internet. It may be commercial or shareware or open source or GNU or whatever — the main point here is software that will be installed and used by thousands or millions of people.

Shrinkwrap has special problems which derive from two special properties:

Since it has so many users who often have alternatives, the user interface needs to be easier than average in order to achieve success.<br>Since it runs on so many computers, the code must be unusually resilient to variations between computers. Last week someone emailed me about a bug in CityDesk which only appears in Polish Windows, because of the way that operating system uses Right-Alt to enter special characters. We tested Windows 95, 95OSR2, 98, 98SE, Me, NT 4.0, Win 2000, and Win XP. We tested with IE 5.01, 5.5, or 6.0 installed. We tested US, Spanish, French, Hebrew, and Chinese Windows. But we hadn’t quite gotten around to Polish yet.

There are three major variations of shrinkwrap. Open Source software is often developed without anyone getting paid to develop it, which changes the dynamics a lot. For example, things that are not considered "fun" often don’t get done in an all-volunteer team, and, as Matthew Thomas points out eloquently, this can hurt usability. Development is much more likely to be geographically dispersed, which results in a radically different quality of team communication. It’s rare in the open source world to have a face to face conversation around a whiteboard drawing boxes and arrows, so the...