Of bits, nibbles, bytes and kilobytes

Every so often a really basic question gets asked that makes us reexamine how computers work. That question had to do with the confusion about bits, bytes, megabytes, and other strange computer terminology.

To start to answer, it must be remembered that our machines are "binary computers." That means that what is going on inside the computer is defined by a series of zeros and ones. (Electrically, these are signals that are either "off" or "on.") These are the two "binary" states. A "zero" tells the computer to do a particular thing. A "one" tells the computer to do something else. It is the only language the computer understands. Each zero or one is a single "bit" of information.

It takes more than a single bit of information to make the computer do something complex. Therefore these zeros and ones get combined into strings of bits. When eight of these "bits" get combined, the resulting string is called a "byte." (A "nibble" is four bits or half a byte.)

As an example, text inside a computer is defined using the ASCII (American Standard Code for Information Interchange) code. There are 128 basic ASCII characters and 128 "extended" ASCII characters. Each ASCII character is one "byte" in length.

My name, Art, in the ASCII code, is defined by three bytes of information: A is 01000001, r is 01110010 and t is 01110100. Therefore, inside the computer, Art is represented by a string of 24 bits of information. Incidentally, sorting inside the computer is accomplished because of the order of these ASCII characters. An uppercase "A" comes before an uppercase "C" and both come before a lower case "a," etc.

When we write a letter or e-mail, the characters inside the computer are represented in this ASCII code. A long letter may contain hundreds or thousands of "bytes" of information.

We use shorthand terms to represent these long combinations. One thousand bytes of information are called a "kilobyte." (For the mathematically inclined, the kilobyte actually is 1024 bytes)

A long letter in Microsoft Word, for instance, could consist of many kilobytes of data since not only are all the words represented, but additional bytes of data are required to tell the program what colors to use as well as other formatting information.

When we start to store lots of these letters and other information, kilobytes are not enough. So, one thousand kilobytes are represented as a "megabyte," or one million bytes. (This is eight million bits.)

What happens when we try to store many pictures, songs or even video? We need more than megabytes of space. So the next term we use is a "gigabyte," or one thousand megabytes.

A modern compact disk can hold around 650 megabytes of data. A DVD can hold over two gigabytes of data.

In our computers, we store all this data on our "hard drives." Modern hard drives now inexpensively hold 80 or 120 gigabytes of data with larger drives coming on the market monthly.

If we were trying to store all the VISA card data, our hard drives would be rated in "terabytes," one trillion bytes, or even "petabytes," or one thousand terabytes.

Lastly, remember that "storage" is where we keep data in permanent form using our hard drives.

"Memory" is where data gets transferred for immediate use in the computer but is lost when the computer is shut down.

If you would like to hear more about terminology, or other computer topics, visit "Coffee and Computers" at the Tustin Area Senior Center, 200 S. 'C' Street, any Friday morning starting at 9 a.m. Bring your questions or just come in and visit.

In the mean time, keep the neurons happy, synapses snapping and enjoy computing.

Dr. Art Holub is a long time resident of Tustin and teaches computer and Internet courses at the Tustin Area Senior Center and the Tustin Adult School. Visit his web site at: This column is written to address the computer adventures and concerns of older adults. If you have comments, questions or suggestions for future columns, Email HIM at:

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