A computer can take information in from a variety of sources, such as a keyboard, or from data stored on a magnetic disk. It then follows a set of instructions, called a program. For example, the program might instruct the computer to take the next letter key you press, and show it on the screen. Or it might tell the computer to shoot the space alien's ship and blow it into a million pieces.

The computer can also send information to a printer, or to a disk, where it can be stored permanently. Information that the computer needs quickly is often stored in temporary memory chips, called Random Access Memory (RAM).

The key to personal computing is that the computer is programmable. That means that it can be loaded with different sets of instructions, to perform different tasks in different circumstances. Instead of having a typewriter, calculator, fax machine, and drawing tablet, for example, you can simply run the appropriate program on your computer so that it will perform the same tasks as these other devices.

Computers use a program called an Operating System (OS) to provide the user interface. Your microwave oven has an operating system, which you interact with by pressing the number buttons. An interface with pictures, for which you use a mouse ( like on your computer) is called a Graphical User Interface (GUI). The OS is always running, and it serves as the medium between you and the "guts" of the computer. You react to what the OS shows you, and the OS translates your typing and mouse-clicks into something that the processor can understand.

Computers use transistors to process data. The Central Processing Unit (CPU) in your computer (similar to the one pictured above) has millions of transistors. The recent Intel Core Duo chip, for instance, has about 150 million transistors. The memory chips in your computer have several million more transistors.

 

 

 

Computers can only understand binary data. A transistor has two states, on or off. A computer uses the number 1 to represent a transistor that is on, and the number 0 to represent one that is off. Everything you see on a computer is, at the deepest level of the machine, just a series of ones and zeroes.

A one or zero on a computer is called a bit (for binary digit). Eight bits make up a byte, which is usually the smallest size increment you will see. 1024 bytes is called a kilobyte (KB); 1024 kilobytes is called a megabyte (MB), and 1024 megabytes is called a gigabyte (GB). A gigabyte consists of 1,073,741,824 bytes, or over 8 billion ones and zeroes. The hard drive of a typical new computer holds over 40 gigabytes worth of data. That's a lot of ones and zeroes!

A computer stores data on a magnetic medium called a hard disk (or you can use a removable floppy disk, zip disk, or tape). When you save your work to a network file server you are in essence saving your work to a big external hard drive. The data stored on the disk can be a program, a picture, a document, or a system file. To make the data useful to you, the computer needs to run a program (like a picture viewer, word processor, etc.). When a program runs, it and the files it needs are moved to a temporary storage area called Random Access Memory (RAM) where it can be accessed at the highest possible speed. The more RAM a computer has, the more programs it can run at once, and the peppier it feels. Most recently-manufactured computers have a minimum of 128 or 256 MB of RAM, and many have more. People who use very sophisticated programs, such as Adobe Photoshop, should have lots of RAM.

People often confuse RAM (which is temporary storage) with hard disk space (which is permanent storage). I like to compare this to doing one’s laundry. The computer’s memory (RAM) is like the washing machine, and the storage space (hard drive) is like the laundry basket. When you have lots of laundry, you can fill up your basket, but keep more laundry elsewhere (another basket, a sack, the floor, etc). This is similar to the way that we can save our computer work on the hard drive, a floppy disk, or the network. But there is a finite amount of wash we can do at once (based on the size of your washing machine) , just as there is only a finite number of programs your computer can run simultaneously (based on the amount of RAM you have installed).

Another area of computer use that confuses some people is the mouse. How many times to click it, which buttons to use, etc., can all be the cause of frustrating mix-ups.

We use the mouse for three distinct purposes:

1. To move the cursor around the screen
2. To select files
3. To open files

Moving the cursor is the most obvious job for the mouse, and doesn't usually cause much difficulty. Sometimes you may not be able to "find" the mouse. In that case, my advice is to move shake it vigorously from side to side for a couple of seconds, and then click (one of) the button(s). This may reposition the cursor where you don't want it to go, but at least you'll be able to find it, and then you can move it back to where you want it to go.

We select a file when we click on it once. An example is when we want to drag a file from one location to the trash can. Click once with the mouse, which tells the computer that you have selected an object, and then you can do something to that object, such as move it.

When we want to open an object, we click twice, in rapid succession. This "double-click", makes sense if you think of it as clicking once to select the object in question, and then opening it with the second click.

It is important that you only double-click when you have to. Otherwise the computer can get confused as to your intentions.

People (usually those who are used to Macintoshes) often seem confused about what to do with the extra buttons on a mouse. My advice is to use the left-hand button for everything you would expect a mouse to do for you, and ignore the right-hand button. The right-hand button is used to invoke what are called contextual menus. The items in these menus change depending on the item on which you click (that is why they are contextual). To see what this means in practical terms, click once with the right-hand mouse button right HERE. Now click once with the right-hand mouse button on one of the pictures on this page. Do you see that your choices are different? You may want to experiment with seeing which options the right-hand mouse button offers you in different contexts, as using the right-hand mouse button often separates power users from novices. But you can get by just fine by ignoring it completely.