Imagine someone asking you if you'd like a Rolex for free. As soon as you nod your head and hold out your hands, he empties a box of tiny gears, levers, cams, and a pair of watch hands into your palms.
"It's kind of a kit," he laughs, like a mad hatter after a tea party.
That's where we've left your understanding of computer hardware. We've talked about all the parts but haven't bothered to put them all together. Worse, we haven't even discussed what holds them all together and gives them what they need to work.
It's not jam or jelly. In this book, we'll call it your computer's infrastructure, because it holds everything together and supplies what you need, much like the infrastructure of a city—the roads, utility wires, and water and sewer pipes that link you to civilization and civilized life. More than that, it's also the foundation that your computer is built upon, the metal and plastic that make up the computer that you can touch.
In the early chapters of this book, we looked at the pieces that make up the electronic circuits that actually make your computer work. We discussed printed circuit boards in the abstract—what they do and how they are made—but stopped short of the prevailing standards that dictate how big they are and how they plug together. That's because your computer would work no matter how engineers fit the pieces together. As long as they take care of their assigned functions, the computer will work.
But if they are not put together, if they lack what we're calling infrastructure, they cannot work, or at least they cannot work together. This infrastructure stuff is an afterthought, but one that's necessary to making things work.
The most important piece of this infrastructure is the motherboard. It holds all the essential circuitry of the computer. On it you'll find the microprocessor, memory, ports, and often the audio and often the video circuits of your computer. The motherboard is the centerpiece where everything comes together.
The circuits that don't fit on the motherboard reside on expansion boards, which plug into slots on the motherboard. The slots are the physical embodiment of the expansion bus. In addition, the motherboard provides the link between the power supply and the circuits of your computer.
The power supply is an essential element to any electronic device. It provides a steady, refined source of electricity for every component in your computer.
Holding all this together is your computer's case. Although seemingly the least-technical part of your high-tech computer, the simple case embodies a remarkable number of functions and technologies of its own. Not only is it tailored to fit the essential circuitry of your computer and its peripherals, it also matches your environment and how you use your computer. What's more, it protects your computer's circuits from that environment—and protects you from its circuits.
Put it all together, and you have a complete computer.