What’s inside a computer?

Question: Most of the stuff you write about is geared to intermediate or advanced computer users. How about some basic stuff for beginners? There are a lot of us new users who need information just for beginners.

Answer: This is a project I have been meaning to do for some time.

While some more intermediate or advanced users may find it overly simplistic, I think it will be a useful reference in teaching folks who are just starting out.

From time to time, I will try to run columns about computer basics. You can take a look at this introductory article on “Computer Basics for Newcomers to Computers” .

So here are a few basic definitions:

Let’s start with a definition of what a computer is, and then look at some key components inside.

A computer is a counting machine. Modern-day computers process information in the form of binary numbers. Binary is a counting system that uses only the numbers one and zero (not zero through nine). A computer is really a glorified calculator that can do millions of binary calculations a second.

These binary calculations together form commands. These commands, all grouped together, tell the computer to do tasks. Programs can contain millions of commands that have the ability to take information from a computer user and do something with it to produce a meaningful result.

There are two types of computers dominating the market—those built by Apple
Computer, usually called Macintoshes or “Macs,” and those referred to as PCs or “personal computers”. PCs were originally designed by Lenovo (formerly IBM)
and are sometimes called “IBM-compatibles”.

Today’s PCs have a variety of different parts, but the majority use Intel processors, which are controlled by an operating system called Microsoft Windows. A computer’s “operating system” is the basic program that controls the computer. Most PCs use Microsoft Windows. Macs use the Mac OS X operating system.

Programs for Macs
do not run on PCs. As a general rule, programs for PCs do not run on Macs. (There is a program called an “emulator” you can use to make some PC programs run on a Mac, and there are a few newer pieces of software that have been adapted to run on Macs.)

So what is a computer made up of?

CPU (or processor): A CPU or central processing unit, also known as just a “processor”, is the brain of a computer. It does all those binary calculations to make programs run. You’ll hear people talk about a “Pentium” or “Athlon” (for PCs) or “G4” (in the Macintosh world). They are referring to the brand of processor in the computer. (For more information about types of processors, please see: “How to choose a microprocessor”.

Hard Drive or Hard Disk: A hard drive is the storage on a computer that contains all the information the computer needs to operate, including programs, data created by a computer user, and the operating system. A hard drive is sometimes referred to as a “hard disk”. It is not that beige or black box that all the computer components are in; a hard drive is actually a bunch of disks spinning very quickly inside a case. There are special “heads” that read and write information onto the disks. The heads are similar in concept to the arm on a record player. They move back and forth over the surface of the disks as they spin. They use magnetism to read and write binary information.

RAM: RAM
is short for Random Access Memory. This is also referred to as simply “computer memory”. This is where the computer does short-term tasks. When a program runs, a copy of it moves off the hard drive and into the processor. Then, when the processor wants to do special calculations or specific tasks, it sends the task to the memory where calculations are made. When that’s done, the task is wiped out of RAM. (For more about how to add memory to your computer, please see our “How to Add RAM” article.

If you “run out of memory”, it means that there are too many tasks in RAM, and no more can fit in. Sometimes these tasks use the same part of the memory and this causes a computer crash. A crash means the computer stops working. When you switch off the computer and restart it (also called “rebooting”), the RAM is wiped clean and the computer should operate normally again. A hard drive is not wiped clean during a restart. It retains all information even when the computer is switched off. To help keep them straight, remember that the hard drive holds data more or less permanently, until it’s deleted by the user, while RAM holds information temporarily, only long enough to assist the program it’s part of.

For more on Computer Basics, see this topic which features several articles on “Computer Basics”.