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On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Previous Week's Question Published: 4 March, 2004 Next Week's Question
Sometimes, a frozen computer needs a good, swift reboot
Question
Why do computers freeze up?

Question
A computer program consists of instructions for the computer to follow, much like a cook follows instructions to bake a cake. There are many chefs inside your computer, trying to get their work done. One chef runs your printer, another your internet browser, and another the game you are playing. The instructions that each chef carries out are so big and complicated that they hire hundreds of other chefs to help them.

The operating system itself, something like Windows 2000, is big and is run by lots of chefs. Some chefs do nothing but supervise other chefs.

With all these chefs trying to do their work at the same time, there are bound to be mistakes. Some mistakes have to do with how chefs interact. Here's one, called a resource allocation problem. Harry and Joe each needs two pots to do their work, and only two pots are available. Harry takes one pot, Joe takes the other, and then they both wait for the second pot. They are stuck, they are frozen, waiting for something they can't have. If Harry and Joe are big chefs, controlling lots of others, then ALL the chefs might end up waiting forever. The work in the kitchen is frozen.

Here's another problem. When chefs are ready to carry out instructions, the instructions have first to be placed in your computer's memory. If there is not enough memory, then someone else's instructions have to be replaced. Your computer might spend so much time swapping instructions in and out of memory that it has no time to get real work done. Your computer seems frozen. Solution? Put more memory in your computer.

Sometimes, your computer freezes because of a hardware problem. Perhaps your hard disk stops working, or your mouse stops working, because of real physical problems.

As you can see, there are lots of reasons your computer might freeze, and sometimes it's hard to figure out why. Often, just rebooting the computer solves the problem.

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