A technical definition of an operating system seems to be fleeting, so I use a practical one: an operating system is whatever the publisher puts on the CD. If they choose to incorporate a whole slew of features which I (personally) don't care about, I will call it feature creep. If the software seems larger than reason dictates, I will call it software bloat. These definitions may seem subjective, but they are what I care about as a consumer.
To give you an example: QuickTime is installed by default on Macintosh systems. In Mac OS X 10.1, the QuickTime framework (ie. the libraries) is about 5 MB. That is sane and may even be reasonable (I don't know how many audio, image, and video codecs it provides). Another component is the QuickTime Player, which is some 15 MB in size. The player is pretty simple, and the hard work is being done by the libraries. Why is it so big? I poke around a bit and find that 88% of that is used for resources: icons and languages. Now I like the appearance of Workbench 2.x and Mac OS 7. Simple, yes. Garish and busy, no. Languages are another sticking point. Yes, it is important for developers to make multilingual programs. Yes, it is important for multilingual support to be available on the distribution media. On the other hand, I only understand one language and I've rarely encountered situations where a given machine would need to support more than two or three languages. So why were fifteen languages installed by default? And the executable itself is still 1.6 MB. Why is it so bloody large when the resources are stored somewhere else, and libraries are handling all of the encoding and decoding. The logic for the program ought to be pretty simple: it involves setting up windows and allowing the user to select function. Something like this would have taken 10's of kB in the past.
Then there are other issues, such as the complexity of the system. I like understand what is going on at a high level. If the system is too complex to even track dependencies, how am I supposed to understand the system at a lower level?
