What's Behind Today's Bloated Code?
Some of the bloat we commonly see in today's software is, no doubt, due to the tools used to create it. For example, a decade ago, low-level assembly-language programming was far more common. Assembly-language code is compact and blazingly fast, but is hard to produce, is tightly tied to specific platforms, is difficult to debug, and isn't well suited for very large projects. All those factors contribute to the reason why assembly language programs--and programmers--are relatively scarce these days.

Instead, most of today's software is produced with high-level programming languages that often include code-automation tools, debugging routines, the ability to support projects of arbitrary scale, and so on. These tools can add an astonishing amount of baggage to the final code.

This real-life example from the Association for Computing Machinery clearly shows the effects of bloat: A simple "Hello, World" program written in assembly comprises just 408 bytes. But the same "Hello, World" program written in Visual C++ takes fully 10,369 bytes--that's 25 times as much code! (For many more examples, see http://www.latech.edu/~acm/HelloWorld.shtml. Or, for a more humorous but less-accurate look at the same phenomenon, see http://www.infiltec.com/j-h-wrld.htm. And, if you want to dive into Assembly language programming in any depth, you'll find this list of links helpful.)

Human skill also affects bloat. Programming is wonderfully open-ended, with a multitude of ways to accomplish any given task. All the programming solutions may work, but some are far more efficient than others. A true master programmer may be able to accomplish in a couple lines of Zen-pure code what a less-skillful programmer might take dozens of lines to do. But true master programmers are also few and far between. The result is that code libraries get loaded with routines that work, but are less than optimal. The software produced with these libraries then institutionalizes and propagates these inefficiencies.

You And I Are To Blame, Too!
All the above reasons matter, but I suspect that "featuritis"--the tendency to add feature after feature with each new software release--probably has more to do with code bloat than any other single factor. And it's hard to pin the blame for this entirely on the software vendors.

Take Windows. That lean 5-Mbyte version of Windows 3.0 was small, all right, but it couldn't even play a CD without add-on third-party software. Today's Windows can play data and music CDs, and even burn new ones. Windows 3.0 could only make primitive noises (bleeps and bloops) through the system speaker; today's Windows handles all manner of audio and video with relative ease. Early Windows had no built-in networking support; today's version natively supports a wide range of networking types and protocols. These--and many more built-in tools and capabilities we've come to expect--all help bulk up the operating system.

What's more, as each version of Windows gained new features, we insisted that it also retain compatibility with most of the hardware and software that had gone before. This never-ending aggregation of new code atop old eventually resulted in Windows 98, by far the most generally compatible operating system ever--able to run a huge range of software on a vast array of hardware. But what Windows 98 delivered in utility and compatibility came at the expense of simplicity, efficiency, and stability.

It's not just Windows. No operating system is immune to this kind of featuritis. Take Linux, for example. Although Linux can do more with less hardware than can Windows, a full-blown, general-purpose Linux workstation installation (complete with graphical interface and an array of the same kinds of tools and features that we've come to expect on our desktops) is hardly what you'd call "svelte." The current mainstream Red Hat 7.2 distribution, for example, calls for 64 Mbytes of RAM and 1.5-2 Gbytes of disk space, which also happens to be the rock-bottom minimum requirement for Windows XP. Other Linux distributions ship on as many as seven CDs. That's right: Seven! If that's not rampant featuritis, I don't know what is.