What Does an Operating System Do?
All computers need an operating system to function. A computer's hardware -- its monitor, keyboard, hard drives and memory -- are like the bones and muscles in your body, which need guidance and direction to function. Your brain -- the operating system -- provides the direction, coordinating all the mechanics of your computer to turn this collection of machinery into a functional tool.
Hardware and Software
A computer has two types of components, broadly defined: hardware and software. The easiest way to understand the difference is that hardware can be touched; you can physically move and interact with it. Software, on the other hand, is virtual, existing as zeros and ones and complex code on your digital media like CDs and DVDs and on your system's hard drive. Your operating system is software, a program that integrates with the basic hardware of your system. You load other software onto your operating system, creating layers of software on your computer.
In most cases, someone else installs the operating system onto your computer. Usually, this process takes place at the factory, before computers are even packaged in boxes and sent to electronics stores or customers. The operating system goes on your hard drive, where all the data on your computer is stored, and integrates itself into your system's boot sector. This is a complex way of saying that your operating system is the first program your computer loads when you turn it on. Computers need an operating system to function at all. Prior to graphics-based operating systems, such as Mac OS or Windows 3.1, all computers used text-based operating systems to read disks and launch programs.
The operating system on your computer uses small software programs called "drivers" to control your hardware. Operating systems have built-in drivers for the more complex hardware on your computer -- like the CPU (or chipset), the hard-drive controllers, the random access memory (RAM) and the universal serial bus (USB) ports -- that let your computer function in a basic way. When you install a new piece of hardware, like a printer, you must install a program to manage it. Drivers aren't exactly part of the operating system, since they're designed by hardware manufacturers and not operating system manufacturers, but the operating system still needs drivers to work correctly.
Your operating system also runs all your computer's applications. Certain applications are designed with a specific operating system in mind, so when you buy or download software, it's important to make sure you're getting the correct version. Programs designed for Windows, for example, won't run on a Mac and vice-versa, so manufacturers usually release two different versions of the software. Similarly, some programs work only on specific versions of Windows or the Mac OS, so check carefully before buying. This caution also applies to purchasing hardware. You don't want to buy a webcam for your Windows 7 computer, for instance, to find that the software accompanying it only works with Windows XP.