Last month I kicked off a series of columns that offer the basics you need to know for computer literacy. That first installment focused on what things are called. You learned computer lingo, and now we're going to put it to good use. This month, let's take a simple look at how a computer works. Just like any other machine, it's a collection of components that work together to do specific tasks. When you turn on your computer, its power supply kicks on, providing energy to the various parts inside. Drives begin spinning, as do fans, which keep the computer cool. Next, the computer's BIOS, or Basic Input/Output System, comes to life. It's software permanently stored in a chip that begins the process of booting up. It checks to make sure all the necessary hardware is in place and working properly, then searches your drives for the operating system. (Modern Macs use a different technology to start up, called the EFI, but it does essentially the same thing.) Have you noticed when you start some computers that its various drives make noises during this process? If your PC is older and has a floppy disk, it may make a grunting sound. You may hear your CD or DVD drive whir. That's because the BIOS is searching for the operating system, and it usually finds it on your PC's hard drive. Once found, the operating system is loaded. This may take a while, depending on the speed of your computer's hardware, the operating system and what software you have installed on it. For example, if you have a lot of programs that load at startup, it will take a while for your desktop to fully load. Now, here's what happens when your operating system starts: Platters and arms The software for the operating system is stored on your hard drive. The drive is actually a series of platters with a magnetic coating, and a series of arms reads the code stored via magnetic impulses. It looks a lot like an old-fashioned record player, but the arms move very fast. The operating system and other software are read from the drive and moved into your computer's Random Access Memory, or RAM. You can think of it this way: Your hard drive is permanent storage, like words on the page of a book. When you open the book and read the words, they are then in your brain's memory, which is like your RAM. When you take notes on a piece of paper, you're saving the words in your mind to 'permanent' storage. Controlling it all Your operating system, once it's loaded, controls how you, your computer's hardware and the software you use all interact. When you launch a program, save a file, play a video or hop on the Internet, the operating system is in control. It also has a big say in what you see on the screen -- how windows look and behave, what happens when you use your mouse and keyboard, what happens when you copy or delete files. Other programs rely on the operating system, too. When you save a file in different programs, have you ever noticed that the window that pops up to start the saving process often looks the same? That's because it's being provided by the operating system, rather than the program you're in. Your computer is one big system, but it's made up of smaller ones. There are subsystems for the video you see and the audio you hear. There's another subsystem that connects to your home network, or to the Internet. Another subsystem handles how your hard drive and CD/DVD talk to the rest of the computer. Overseeing all this is your computer's processor, or CPU. Based on instructions in the software you're using, it directs information to different places. The processor is plugged into a large circuit board called a motherboard, and everything else plugs into it, too. It's where all the computer's systems talk to each other. Of course, this is an oversimplified description of how your computer works, but it should be enough to help demystify your machine. The next time you start your computer, you'll know the basics of what's happening inside. Next month, we'll look at the parts of the computer you touch most often: the mouse and the keyboard. dwight.silverman@chron.com? blogs.chron.com/techblog? twitter.com/dsilverman XXX - End of Story3D 