Therefore, it has an impact on your options with these important components as well.
The system case, sometimes called the chassis or enclosure, is the metal and plastic box that houses the main components of the computer. Most people don't consider it a very important part of the computer (perhaps in the same way they wouldn't consider their own skin a very important body organ). While the case isn't as critical to the system as some other computer components (like the processor or hard disk), it has several important roles to play in the functioning of a properly-designed and well-built computer.
The case doesn't appear to perform any function at all, at first glance. However, this isn't true; the case is in fact much more than just a box. The case has a role to play in several important areas:
Structure: The motherboard mounts into the case, and all the other internal components mount into either the motherboard or the case itself. The case must provide a solid structural framework for these components to ensure that everything fits together and works well.
Protection: The case protects the inside of your system from the outside world, and vice-versa. Vice versa? Yes, although most people don't think about that. With a good case, the inside of your computer is protected from physical damage, foreign objects and electrical interference. Everything outside of your computer is protected from noise created by the components inside the box, and electrical interference as well. In particular, your system's power supply, due to how it works, generates a good deal of radio-frequency (RF) interference, which without a case could wreak havoc on other electronic devices nearby.
Cooling: Components that run cool last longer and give much less trouble to their owner. Cooling problems don't announce themselves; you won't get a "System Cooling Error" on your screen, you'll get random-seeming lockups and glitches with various parts of your system. You'll also have peripherals and drives failing months or years before they do on your friend's computer, and you'll never even dream that poor cooling is the cause. Making sure that your system is cooled properly is one good way to save yourself time, trouble and money.
Note: A spacious, well laid-out case is a critical part of proper system cooling. Small cases require components to be packed close together, which reduces cooling in two ways. First, air-flow through the case is reduced because it is blocked by the components. Second, the parts are closer together so there is less space for heat to radiate away from the devices that are generating it.
Organization and Expandability: The case is key to a physical system organization that makes sense. If you want to add a hard disk, CD-ROM, tape backup or other internal device to your PC, the case is where it goes. If your case is poorly designed or too small, your upgrade or expansion options will be limited.
Aesthetics: The system case is what people see when they look at your computer. For some people this isn't important at all; for others it's essential that their machine look good, or at least fit somewhat into their decor. In an office environment, PCs that all look different can give a work center a "hodge-podge" appearance that some consider unprofessional, for example.
Status Display: The case contains lights that give the user information about what is going on inside the box (not a lot, but some). Some of these are built into the case and others are part of the devices that are mounted into the case.
In terms of its actual operation, the case doesn't of course do a lot. It does have switches and the above-mentioned status lights.
Your computer is obviously an electronic device, and its many components of course require power. Like the case, most people don't give much thought to the power supplied to the system. The power supply in your PC can be compared to the officials at a football game: if they are doing their jobs properly nobody really notices them, but if they aren't, everybody knows it and lets them know about it.
There are two aspects to power in the PC:
External Power: External power refers to the power that is delivered to the back of the system case. There are several considerations regarding this power and how it is supplied that will determine if your internal power supply is going to work the way it should.
Power Supply: The power supply is the small box that sits inside your case and takes the external power you supply to the computer. Its main job is to transform this power into a form the rest of the computer can use.
The Power Supply
The internal power supply is responsible for converting your standard household power into a form that your computer can use. The power supply is responsible for powering every device in your computer; if it has a problem or is of low quality you may experience many difficulties with your PC that you may not realize are actually the fault of the electrical system. The power supply plays an important role in the following areas of your system:
Stability: A high quality power supply with sufficient capacity to meet the demands of your computer will provide years of stable power for your PC. A poor quality or overloaded power supply will cause all sorts of glitches that are particularly insidious, because the problems occur in other, seemingly unrelated, parts of the system. For example, power supplies can cause system crashes, can make hard disks develop bad sectors, or cause software bugs to appear, problems which can be very difficult to trace back to the power supply.
Cooling: The power supply contains the main fan that controls the flow of air through the PC case. This fan is obviously a major component in your PC's cooling system.
Energy Efficiency: Newer PC power supplies work with your computer's components and software to reduce the amount of power they consume when at a idle.