Talk About Quality

Tom Harris

Archive for September 2010

Change the Software

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Recently I became the unwitting user of a new piece of consumer software, when our office upgraded our mobile phones. Suddenly, with every phone call, appointment reminder, and even when charging the phone, I’m acutely aware of what I want from this piece of embedded software that I did not even buy. As a software user I want only two things: more or better features, and problems fixed. I don’t care what version the software is — I care what’s changed. It would make sense, then, that software developers should focus on changes, not versions, and that tools should support them.

The most common tool on a software development project is always the “bug tracker” or defect tracking system. It’s really a change request tracking system, with two kinds of requests for changes: enhancements (performance improvement or new feature requests) and defects (fix requests). Tracking requests for changes. That’s good.

Now look at the other major tool in every software development group — it’s usually called a “version control system”. But see above —  users don’t care about versions. And developers have to report to the defect tracking system what they’ve done, and that system is which is full of requests for changes, not requests for versions. So why would we want a version control system?

That’s why the light went on for me when I read Joel Spolsky’s Hg Init: a Mercurial tutorial. Not because Mercurial (or Git) makes branching cheap and merges easy. (It does.) But because, as Spolsky writes:

Subversion likes to think about revisions. A revision is what the entire file system looked like at some particular point in time. In Mercurial, you think about changesets. A changeset is a concise list of the changes between one revision and the next revision. (When Spolsky writes “revisions”, read “versions”.)

Now I understand why there’s so much trouble connecting our defect (change) tracking and version control workflows. Testing too — what we really want to know is, “Which change broke the build?” And bringing in code review, more problems, because people want to review whether each change accomplishes the goal of adding or fixing something.  Software development is all about changes: specifying them, designing them, coding them, testing them, and delivering them. Not versions. Changes. Sure, versions have a place in software delivery — they are labels for the software after a certain number of changes. (Mercurial supports them, as “tags”.) So if you want all the tools to work together and make your software development life easier, switch to a software repository that lets you control changes.

What should we call them? Maybe “software changeset control systems”. The two big ones these days are Mercurial, and Git. For Mercurial, see Spolsky’s tutorial. For Git, listen to Linus Torvalds on git.

Written by Tom Harris

September 15, 2010 at 11:11 pm

Posted in Testing

Software is Writing

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Software is not construction

Software is not construction, no matter how popular that statement may be. A program is not a building. Parts are not chosen first and then fitted into place. Design continues almost to the last minutes of coding. Further, almost nobody spends time creating new code, at least not for very long. Sure there are new products and new codebases. But even then, after a short period, most additional coding is extending or changing an existing codebase. So if coding is not construction, and mostly involves changing what’s already created, what is it?

Well, coding is writing. It’s using text to communicate a message. That may not sound like much, but understanding this helps a lot. Instead of struggling to make up new ways of thinking and learning, as if programming were a completely new human activity, we can look at how good writers write. People have been writing for many hundreds of years, and have become pretty good at it.

Learning to write

How do people get into writing? Do we start, as most do in programming, full grown, writing essays? No, not at all. We start as children, and learn first to talk, then to read, and finally to write. Yes, I know that school seems to teach writing, at least forming the letters, before reading. But it’s an illusion: listening to a bedtime story is essentially reading – paying attention to someone else’s writing, and understanding it – and comes before writing. Most people don’t try writing that communicates a message – expository prose – until secondary school or later.

Good writers have their audience in mind at all times. They edit their writing through several drafts, as well as getting others to review it, and give written comments. And they talk about their writing. Maybe not always directly, but when a political columnist goes to a dinner party, you can bet he’ll talk politics. When a novelist chats in the park, she’s talking about the same human struggles that will later appear in her books. Even for the solitary writer typing in a darkened room, the life that feeds the writing is one of talking with, listening to, and reading about people.

Software is Writing

Now back to software: software is not like writing, it is writing. In our industrial setting, it is too late or too radical to suggest re-teaching programming, by teaching first how to talk, then to read, then to write programs. But we can highlight where daily programming work already involves each of these three activities, and where it doesn’t, but should.

Talking includes formal design reviews and code reviews, but also whiteboard conversations and hallway arguments. How should I write this here? Why is that data structure that way? Why does the compiler give that warning? Don’t just think alone – talk it out with someone nearby. It is the same with tests. Why does that scenario fail intermittently? How should I write it differently? And even for defect entries -what does the submitter really mean? Phone him up. Why does this change fix the problem? Find the developer and ask.

Reading is for design documents, training materials and perhaps professional books. But mainly, it includes reading lots of existing code. That’s reading it until you’re really sure what it does, so you know how to change it, fix it, extend it. There is also code review — where the author asks you to read their code, not just to say that it looks fine, but to identify what’s wrong, or unclear.

Writing is the coding, of course. But who is the audience? There are two audiences. One, the compiler, which is your personal translator, from a non-native language (nobody’s mother spoke to them in C), to an almost unknown language – the machine language that the hardware actually understands. The compiler is a rigid, simple-minded, sometimes unpredictable audience, just a ghost of the person who wrote it. Here you have to be very precise, careful, and limit yourself to what the compiler understands and to what the hardware will accept. The other audience, is so very different – the next developer. This may be yourself a few weeks later, or someone else, but there will always be another developer, coming back months or years later, to fix or extend the code. She wants comments, explanations, meaningful names for things, and an easily readable structure. Because now you’re long gone, she can’t talk to you: she must read, so you must write.


Well, with all this talk about programming being writing, let’s come back to earth. Software developers are technical people, and expect to use the best tools to do their jobs. There’s the whiteboard in the hallway — we need more of those, for talking. Defect tracking systems, where we can make sure we write clear resolution notes. And for automatically sharing and discussing code, web-hosted code tools for static analysis and code review are the way to go.

Originally published in company internal newsletter. Edited and released here with permission.

Written by Tom Harris

September 15, 2010 at 1:51 am

Posted in Software, Writing