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Lesson 1: History of Computers

Throughout time, humans have invented ingenious calculating machines. One of the earliest was the abacus. It's about 5,000 years old. Mechanical calculators that could add and multiply (but not subtract!) were invented in the 1600s. In 1820, Charles Xavier Thomas de Colmar invented the arithmometer, a machine that could add, subtract, multiply, and divide. It was Charles Babbage though, in the early 1800s, who designed mechanical calculating machines that were the true ancestor of today's computers. Ada Byron King (Countess of Lovelace) was his programmer and today is considered the mother of computer programming.

Babbage's design for his ultimate calculator, the Analytical Engine, was never produced. It did anticipate the four components essential to modern computing. These components are input, storage, processing, and output.

The problem with Babbage's and other mechanical calculators was just that—they were mechanical. The moving parts they relied on were slow and subject to breakdown.

What made modern computers possible was the invention of something that could do calculations and other information processing with no moving parts and do it very fast. That something was electronic components. With electronic components, a fast and efficient machine such as Babbage proposed could be built with all four components essential to modern computing.

Lesson 2: Four Components of a Computers

A computer processes information. A toaster processes bread. Although it's a simpler device, a toaster is a good way to demonstrate the four components of computer processing: inputstorage, processing, and output.

Both a toaster and a computer have physical parts you can touch such as the keyboard and mouse. We call these parts hardware.

Here the similarities between toaster and computer end and the differences begin. Only the computer has something called software that enables it to figure out what to do with the input you give it. You can't touch software. Software gives the computer the ability to process many kinds of information. In contrast, all a toaster can process is bread (and the occasional waffle).

Another difference is a computer has a microprocessor. The microprocessor is the device in the computer that performs most of the tasks we ask the computer to do—from playing computer games to graphing the number of people who prefer cricket to curling. The microprocessor reads and performs different tasks according to the software that instructs it. This ability is what makes the computer such a versatile machine.

The key thing to remember is this: both computer and toaster have four basic components to how they operate (input, storage, processing, and output.) Unlike the toaster, the computer is unlimited in the things it can do.

Lesson 3: How Computers Get Input

Computers are information processing machines. That means that you can use them to access and change information like numbers, text, pictures, and even music. Think of what you can do to modify a single sentence. Using the computer, it's easy to add, delete, or rearrange words. To change a sentence with your computer, though, first you have to get the sentence into your computer.

Input devices are used to put information in your computer. You type a sentence on your keyboard and it goes into the computer. You speak into a microphone and your computer records your words. You make funny faces at the video camera and your computer records every one of them. Even the mouse you are about to click to move on to the next section is an input device. So, when you are ready, click it!

Lesson 4: How Computers Store Information

When you use a telephone, it does not store information. You speak into the phone, the person on the other end hears what you say and then your words are gone. An answering machine is different. It answers the phone and stores the information given by the caller.

To process information, computers need to be able to store it. Otherwise, like the phone, information would come and go before anything could be done with it.

Computers store all kinds of information. They store the information you give them, instructions from the software you're using, plus the instructions they need to operate. To store all this, they use two basic kinds of storage. Temporary storage is for information actively being used for processing. Random Access Memory (RAM) accepts new information for temporary storage. Long-term storage is for information computers use again and again, such as the instructions the computer prepares itself with every time you turn it on. These instructions are stored in read only memory (ROM), a type of memory that does not accept new information.

Computers also use a variety of devices to store information that isn't actively being used for processing. For more information, explore hard drivesoptical discsstorage, and removable media in the site glossary.

Computers Need to Remember, Too

Just as you need to remember how to add when you face an addition problem, computers also rely on memory. A computer needs an addition program in its Random Access Memory (RAM) to "remember" how to perform addition. When the user switches to a word-processing program, the computer can check spelling because the word-processing program is now in RAM.

Some things come automatically to humans. When you breathe or move your arm, you do so without having to remember how your muscles work. Computers have a kind of built-in memory, too. It is called read only memory (ROM). ROM remembers only what it has been programmed to remember at the time the ROM chip was manufactured. "Read only" means it can never be told to do something different after it has left the factory. That would be like trying to reprogram you to breathe water instead of air.

Different Kinds of Storage Media

Computers use Random Access Memory for the information they currently need to do a task. Parts of the program you are currently using and the data you are manipulating are held in RAM while you are working with them. But what about the rest of the programs and information on your computer? They are stored in a variety of other media. You are probably familiar with many of the ones shown on this page. What you might not know is the amazing amount of information some of these can hold.

Lesson 5: How Computers Process Information

Computers use integrated circuit to process information. Of the many chips in a computer, the microprocessor is the most complex. It is where the information you give a computer is processed.

A simpler kind of chip is used to make DVD players, remote controls, and electronic calculators. The chips in these devices are embedded processors. They're made to do one thing well and the instructions are coded into them. You can't install new software to change what they do. For example, you can't do word processing on your VCR.

Microprocessors are much more versatile than embedded processors. Change the software you're using and you can go from doing word processing to playing a computer game. Change the software again and you can explore the Internet. Instead of being designed to do one thing, microprocessors are designed to do whatever the software you select instructs them to do.

Lesson 6: How Computers Deliver Information

All the processing power in the world wouldn't matter much if you couldn't get output from a computer. You're looking at output right now on your screen. You told the computer you wanted to view this page and the software and microprocessor inside it responded by putting the page on your monitor.

Other kinds of output include sound from your computer's speakers and documents printed by your printer. Output can also include things like MP3 files. They allow you to download music from the Internet onto an MP3 player you can take with you anywhere.

Lesson 7: Which Is Smarter?

Computers are sometimes called electronic brains. But are they really brains? Let's compare.

First, let's look at how brains and computers work. A brain uses special cells called neurons that work together to process information and respond with an action. A computer uses a collection of circuits called a microprocessor. One is living cells, the other is electronic circuits. So there's a big difference there.

Now let's consider which is smarter. The answer depends on how you define smart. If smart is speed, a computer wins. A person takes a few seconds to add two 3-digit numbers (245+987). A computer can complete several million long-division problems (387÷243) in a single second. A computer is also tireless. The electronic circuits don't wear out. A human doing long division all day would want lots of breaks—and a good night's sleep.

What if smart is having a good memory? In that case, a computer wins too. A computer can store an entire library of books in its memory and recall them without a single mistake. Now consider a person. Have you ever tried just to memorize a long poem? It's an enormous task for a person to memorize a book.

What if being smart is being able to make well-reasoned decisions? Here a person wins by a huge margin. Computers can only calculate and sort information based on the software we design for them. How good their choices are depend on how good the software is. Compare this to a person. Humans don't need software. We can sort and calculate facts using our knowledge and experience. We also can make judgments and decisions based on whatever facts we're confronted with—not just the facts a computer has been programmed to recognize. In this way, we're a lot smarter than computers.

What if you define smart as the ability to think original thoughts? Here again, humans have an enormous advantage. Humans think original thoughts every day. The evidence of these thoughts is in the inventions, art, and books all around us. The computer is one such invention. Are computers capable of original thought? So far, they're not. Artificial intelligence is a field of science devoted to developing devices that someday may be able to reason and solve problems. It's important to remember though that no matter how "intelligent" we make computers, they will only be as smart as the software we humans create for them.

Want to Learn More?

Explore these links to learn more about how computers work.

How Stuff Works: Computers ›

Online Museum of Computers ›

Computer Quiz ›