> write programs that do one thing and do it well. Write programs to work together.

ASIDE: Just been reading The Wealth of Nations, and Smith talks about the "division of labour", which is similar to this specialisation. By concentrating on one task, a workman can increase his dexterity at it, not waste time switching between tasks, and find ways to do it better. "Do one thing and do it well" is a pithy exaggeration of this specialisation.

This division of labour is only possible because of trade: other workmen do the tasks that you aren't doing, and you barter with each other to get what you each need. Because you specialised, you each do your own task more efficiently, so you are both better off. Programs that "work together" is similar, because if you couldn't use another program, you'd have to include it in the first program. "Programs" would also include 3rd party libraries and frameworks I think.

He goes onto say that one limitation on how much labour can be divided is the market size: you to be able to trade what you make. If people don't need much of what you produce, you've over-specialised. However, if you have access to a large enough market, then in aggregate, with many people using a little bit, you can survive. Larger markets therefore allow more specialisation, and
therefore more wealth. Rich civilisations grew up around navigable rivers (especially with canals), and inland seas (calmer and safer to navigate than the open ocean), because water-carriage facilitates trade with more people (larger market), over larger distances, at lower transport cost and less risk.

Does the analogy fall down with free programs, since you won't go out of business just because few people use it? Open source projects do seem to need users, for encouragement, bug reports, spreading the word, contributing bug fixes etc - users pay in attention, not money. Without attention, projects die.

Does the analogy fall down when it's the same person writing all the separate programs? You can certainly specialise, and therefore do a better job; and also "exchange" data between those parts. (Provided of course that specialisation is actually more efficient, and outweighs the costs of exchange). But the motivation doesn't apply in quite the same way, since the parts of the code don't get paid - not in money, not in attention. You're more like a communistic planned economy (or, within a firm).

But the interesting point I've been leading up to is: does a larger market for programs lead to greater specialisation? For example, Java has a large number of users, and has a ton of 3rd party programs - and that does seem to include very specialised libraries.

Or, are other factors at work, leading to more one-package programs, such as Word; or dividing the market into smaller ecosystems, such as Java itself, and also other languages python/ruby/PHP, and even frameworks, like RoR. There are barriers between these "markets", in the extra difficulty of using library from one platform in another. For example, for JS, I get the impression there are many libraries for doing the same web/forms/template etc. While competition is healthy, and these frameworks are definitely improving on each other, they aren't the "division of labour" of interest to this particular discussion.

In programs, does a larger "market" of fellow coders result in more specialisation in the "one thing" done well?