If you have been shopping for a computer, then you have heard the word "cache." Modern computers have both L1 and L2 caches, and many now also have L3 cache. You may also have gotten advice on the topic from well-meaning friends, perhaps something like "Don't buy that Celeron chip, it doesn't have any cache in it!"

It turns out that caching is an important computer-science process that appears on every computer in a variety of forms. There are memory caches, hardware and software disk caches, page caches and more. Virtual memory is even a form of caching. In this article, we will explore caching so you can understand why it is so important.

A PC is a general purpose tool built around a microprocessor. It has lots of different parts -- memory, a hard disk, a modem, etc. -- that work together. "General purpose" means that you can do many different things with a PC. You can use it to type documents, send e-mail, browse the Internet and play games.

In this article, we will talk about PCs in the general sense and all the different parts that go into them. You will learn about the various components and how they work together in a basic operating session. You'll also find out what the future may hold for these machines.

Let's take a look at the main components of a typical desktop computer.

• Central processing unit (CPU) - The microprocessor "brain" of the computer system is called the central processing unit. Everything that a computer does is overseen by the CPU.

• Memory - This is very fast storage used to hold data. It has to be fast because it connects directly to the microprocessor. There are several specific types of memory in a computer:
• Random-access memory (RAM) - Used to temporarily store information that the computer is currently working with
• Read-only memory (ROM) - A permanent type of memory storage used by the computer for important data that does not change
• Basic input/output system (BIOS) - A type of ROM that is used by the computer to establish basic communication when the computer is first turned on
• Caching - The storing of frequently used data in extremely fast RAM that connects directly to the CPU
• Virtual memory - Space on a hard disk used to temporarily store data and swap it in and out of RAM as needed