You probably noticed that the printed circuit boards in your computer are covered with scores of little rectangular bugs with many legs. These are I.C. chips. I. C. stands for Integrated Circuit. If you could look inside one with a magnifying glass you would see what looks like a downtown map. This is a pile of semi-conducting photographic images that form complex electronic circuits. Each IC can replace thousands of transistors. The contents of any one of those ICs in your computer would have filled a large room with 1942's finest technological equipment.

ICs can do many things. Some are ROM chips, which stands for Read Only Memory. Memory of this sort is like a newspaper. You can read it as often as you like, but you can't change the news.

Others are RAM chips. RAM means Random Access Memory. These chips can be told something and will remember it. If you tell them something different, they will then remember the new information. They only work when the power is on. If you turn the computer off, the RAM chips forget everything.

Other chips are decision-makers. Their individual thinking power is limited, but they team up to control the operation of your computer.

There is one special IC called the CPU, which stands for Central Processing Unit. It is often the largest bug in the box, with the most legs. Almost every bit of information the computer handles is controlled by this chip. Many modern CPUs are covered with fins or a fan to dissipate the heat they generate. (Thinking is hard work!)

Intel is the most well-known manufacturer of CPUs for IBM-compatible computers. In the first IBM-compatible home computers, called XTs, the Intel CPU model number is 8088. In AT-class machines it is 80286, and these more powerful computers came to be known as '286's. In '386' computers the chip number is 80386 and in '486s'... you guessed it. (80486) Pentium chips, more powerful than '486s, no longer follow the numbering convention, but are still sometimes called "586" chips.

Macintosh computers have different numbering and naming systems, but the types of chips, and the general way they work is the same.

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