A computer is an electronic machine which processes information. People can use a computer to do many different kinds of jobs, some of which would be very boring or would take a very long time to do by hand. A computer is only able to follow instructions provided by people. A computer cannot do a job without first being given detailed, step-by-step instructions telling it how. These instructions must be correct so that the computer can do the job correctly.

REVISED 09/04

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A computer program is the series of step-by-step instructions a computer follows to do a job for us. A computer program is first loaded from the hard drive and stored in the computer's memory, or RAM. The computer then follows the instructions exactly as they are written. The computer program is written by a person called a computer programmer. A professional computer programmer writes the programs (designs the software) we use in our own computers at home, at school, or at work. These programs are called computer software or applications, and are usually installed, or loaded, onto our own computer's hard disk. Some people learn to write their own programs.

A computer can only do work for us if we put a program into its memory. A program can be installed from a floppy disk or CD, downloaded through a local network or the Internet, or typed in at the keyboard. This program tells the computer exactly how to do the job. The computer programmer, not the computer, figures out how the job will be done.

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Data may be text, numbers, sounds, or images that a computer can process. Data is input to the program. The program needs data to do a job for us. When finished working with this data, the program sends out the answers or results. This is the output. Data is input and information is output.

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Let's assume that we write a program which enables the computer to take names in a mixed-up order and sort them into alphabetical order. A computer can do this job very quickly. The data used by this program is a list of names in any order. This data is the input for the program. The output of this program is the same list of names in alphabetical order.

The second example shows a computer figuring out an average. The input is a group of numbers and the output is their average.

INPUT:	OUTPUT:

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Hardware is the computer itself, and all the peripheral equipment used with it. The keyboard, the mouse, the display monitor, the hard drive, flash memory, the CD-ROM or DVD drive, the modem, and the printer are the hardware devices we use most often. Other hardware devices include the graphics tablet, the speech synthesizer, the touch screen, the joystick, the floppy drive, the Zip drive, the microphone, and the scanner. Hardware is a part of the computer you can touch.

 

Software is a computer program in the computer's memory or stored on a floppy disk or CD. Application software is made by software companies and is sold to us for use in our own computers. Teams of professional computer programmers design this software. Software is a critical part of the computer, but unlike hardware, it is not tangible (touchable). To understand this, think about a noun. A noun is a person, place, thing, or idea. An idea is real, but you cannot touch it. Software is like an idea, real but impossible to touch. You can touch the CD-ROM on which a game is stored, but you cannot actually touch the game.

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An operating system or OS is software that makes it possible for the computer hardware to communicate and operate with the computer software. It enables the computer to communicate with peripheral devices such as keyboards, mouses, printers, scanners, and modems. Without a computer operating system a computer would be useless.

Examples of computer operating systems include Windows, MacOS, and Linux.

When we buy a computer, it comes with an operating system already installed. PCs usually come with a version of Windows (such as Windows XP) and Macintosh computers come with a version of the MacOS (such as MacOS X). Linux is becoming more popular as an alternative to Windows.

Other devices, such as handhelds and mobile phones, also have operating systems to make them work. These are not computer operating systems. Examples are the PalmOS, Windows Pocket PC, and the Windows Mobile Smartphone OS.

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Input (Data) ----> ----> Output (Information)

Special hardware devices are connected to the computer so that programs and data can be put into or sent out from its memory.

Hardware used to place information into the computer's memory is called an input device. A keyboard is an input device because we use it to type data and programs into the computer's memory. A graphics tablet is also an input device. It is used for placing our own drawings into the computer's memory.

A printer is an output device since it is used to get data out from the computer's memory. A display monitor is also an output device because the computer sends data to it and we read this information from the screen.

A disk drive (hard, Zip, floppy, RAM disk, or rewritable CD or DVD) is used for both input and output. A disk drive is an input device when we read a program or data from a disk and load this into the computer's memory. A disk drive is an output device when a program or data are sent from the memory and are copied onto the disk for storage. A modem is also used for both input and output.

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The computer has three main parts:

1. The Processor: The processor is the computer's "brain". It is sometimes called the Central Processing Unit or the CPU. In a personal computer, the CPU is a computer chip called the microprocessor.

2. Memory & Storage: The memory of the computer is made up of ROM chips and RAM chips. ROM (read-only memory) chips "remember" information permanently. RAM (random access memory) chips remember information only while the computer is running. They "forget" all their information when the computer is switched off. This is why we save our documents or files onto a data disk or onto the hard disk before shutting down the computer.

Information can be stored in different ways.

A. A hard drive is capable of storing large amounts of information inside the computer. It stores information in a non-removable drive using magnetic heads on thin disks.

B. A floppy disk, like a hard disk, stores information magnetically, but only a small amount. Due to this size limitation, floppy disks have decreased in popularity. A floppy disk can be removed and the information moved to another computer.

C. CD-ROMs and DVD-ROMs are removable and can store larger amounts of information permanently. CD-RW and DVD-RW also offer large, removable storage, but the information can be removed from them (similar to a floppy disk).

D. Flash-RAM disks (also known as jump drives, micro drives, and pen drives) are the newest type of memory storage. These plug into the USB port of a computer and can range in size from 16 MB (16 megabytes is equal to about 12 floppy disks) to 4 GB (about 3,000 floppy disks!) and are about the size of a keychain. These disks offer removable large storage that can be erased. Also, these transfer data very quickly and are much less likely to be damaged by accident than a CD-ROM.

3. Input/Output: The input/output system consists of all the hardware devices we connect to the computer so that we can communicate with it. Using these devices, we can put data into the computer's memory, and we can get information out from the computer's memory.

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Our computers are called desktop computers or personal computers (PC's). Desktop computers may be used in many different ways:

They may be used to run programs we wrote ourselves. We can learn to design software to let the computer do jobs for us. Maybe we would like to write a program to figure out our test average for the term or to draw a picture. We would write the program using a programming language and we would save it onto the hard disk.

BASIC and Logo are two programming languages which may be used with our computers. Other popular programming languages include C++, COBOL, FORTRAN, HTML, Java, and Pascal.

Our computers are most often used to run application software. These are the programs on disks or CDs that we buy in stores, order from catalogs, or download from Web sites over the Internet. These programs were written by professional computer programmers. We buy these programs to allow our computers to do many different jobs for us:

1. Word processing software can make the computer behave very much like a typewriter, but even better. One example of this software is Microsoft Word.

2. Database software lets the computer organize lots of information for us. This program allows us to quickly sort through large amounts of data for key pieces of information. A computer used in this way could take the place of a filing cabinet, file folders, and lots of paper. An example of database software is Microsoft Access.

3. Instructional software can make the computer become a teaching machine. We can learn or practice our math, science, history, language arts, reading, and many other subjects by using the right instructional software. This software can be much better than learning from a book because it can ask us a question, wait for our answer, and then tell us if we were right or wrong. Sometimes, it even keeps track of our learning progress. Mavis Beacon Teaches Typing is a good example of this type of software.

4. Everyone likes entertainment software. These are the computer games we play for fun, like "The Sims." Sometimes games are combined with instruction to make learning more fun. This is sometimes called edutainment. A good example of this software is Reader Rabbit.

5. Simulation software can help us pretend that something is happening when it really isn't. A flight simulator, for example, can help a future pilot practice flying an airplane without really leaving the ground. Sim City and Sim Tower are examples of simulation software.

6. Graphics software is used to help us draw or paint pictures. Using a mouse or a graphics tablet, we can produce artwork which might be neater than we could do by hand. There are many different programs that allow this, such as Paint or KidPix.

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What do a pile of rocks, an abacus, and a paper and pencil have in common? They were all used for counting and for solving math problems long before the computer was invented. The adding machine was also used before computers were invented for doing lots of calculations much more quickly than could be done "by hand."

When the computer was invented in 1941, it could do more complicated problems and lots of other jobs, and it was much faster. However, the first computer was huge and extremely expensive.

A very important invention in 1948 made it possible to build smaller, lighter, and less expensive computers. This invention was the transistor. Later, in the 1950's, the integrated circuit was invented. Sometimes called the "computer chip," it contains many electrical circuits and tiny connections. Today's integrated circuits can be even smaller than your fingernail.

In 1970, the first microprocessor was made. Without this invention, the desktop, portable, and handheld computers we use would not be possible. A microprocessor is actually a whole computer on a single chip. A single chip now contains the same amount of "computing power" that took tons of equipment in years past. In fact, the computer you use every day in school is more powerful than all of the computers that ran the Apollo moon mission in 1969.

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1. Mainframe computers are very large computers used by banks, insurance companies, the Pentagon, and other large businesses. These computers are often seen up against walls in movies, because they are too large to put on a desk or under a table.

2. Desktop computers or personal computers (PC's) are now used to do many jobs, large and small. Often, a series of desktop computers is connected together to form a powerful network. Desktop computers arranged in client-server networks are gradually taking over many jobs once done by mainframe computers.

Most of the computers in our school are desktop computers, and most of them are connected through a local network. There are two main types of desktop computers: Macintosh (made by Apple Computer) and PC's (made by many companies such as Dell, HP, Compaq, etc.).

3. Portable computers, among the smallest and lightest computers, are able to run on batteries. They include laptop, notebook, powerbook, and iBook computers.

4. Handhelds and PDAs (personal digital assistants) are computers small enough to hold in one hand. Examples include the Palm, Handspring, and Sony.

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When we connect computers together with cables or using wireless hardware, we are creating a computer network. Programs and data can easily be sent and received by computers through a network. These networked computers are able to work separately or together.

Some networks are small and have only a few connected computers. You might even have a small network in your house. Large networks may have hundreds or even thousands of connected computers, as does our school system.

If the computers are all in the same room or building, the network is called a local area network (LAN). If they are located in different buildings and in different cities, the network is called a wide area network (WAN).

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The Internet is a huge computer network which connects many smaller networks and individual computers throughout the world. These connected computers are located in places of business, in schools, and in people's homes. The Internet has been called a network of networks. Every day, more and more computers are being connected through the Internet.

An important reason people connect their computers through the Internet is to have the ability to send and receive electronic mail, or e-mail. E-mail is a convenient way for people to communicate with each other.

The World Wide Web (www) is another very popular and important part of the Internet. People, companies, and organizations put up Web sites (Web pages or home pages) from which others can get many different types of information. Search engines are available to help people find what they are looking for on the Web. Popular search engines include Alta Vista, Google, Ask Jeeves, Northern Light, Excite, Lycos, and Yahoo!. Search engines designed for kids include Ask Jeeves for Kids (www.ajkids.com), Searchopolis (www.searchopolis.com), and Yahooligans (www.yahooligans.com).

By connecting to Web sites, people can find news, entertainment, weather forecasts, telephone numbers, and state and city maps. They can find information about travel, religion, art, science, sports, health and fitness, gardening, hobbies, clubs, businesses, investments, and much more. No matter what a person's interest, he or she can find information about it on the World Wide Web.

Because it is so easy to find information on the World Wide Web, you must be very careful about what kind of information you put about yourself online. You should never put your name, address, phone number, or any other personal information where someone you don't know can get it.

Moving from page to page on the World Wide Web is easy. Clicking on special words or pictures, called hypertext or hyperlinks, a person can "navigate" to related Web pages. This is how Web pages are "linked" together. Sometimes, people move quickly from page to page on the Web. This is called "surfing the Web".

Some people become connected to the World Wide Web by subscribing to an online service, such as America Online or CompuServe. Others connect directly through a "provider" such as Comcast.

Popular browser software for navigating the World Wide Web includes Netscape Communicator, Firefox, Internet Explorer, and Safari.

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