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Bits and Bytes : An Explanation

by Oscar Sodani
February 21, 2003

Oscar Sodani is a founder of Help2Go and owner of Help2Go Networks, an IT consulting firm in the Washington D.C. area. Oscar holds the CISSP certification as well as industry certifications from Microsoft, Cisco and Novell.

Bits. Bytes. Kilobytes. Megabytes. Gigabytes. Terabytes. You're owed an explanation. Here it is.

In this article, we hope to show you:

  • How a computer stores information
  • The difference between a bit and a byte
  • The storage capacity of some common devices

The Lonely Bit

A computer is an electrical piece of machinery. Just like your light bulb, the circuits in a computer have two states: on and off. "On" is represented by the number 1, and "off" is represented by the number "0". When your computer stores information in its memory banks and on your disk drive, it can record only 1's and 0's. Each one or zero is called a bit. It's the smallest unit of information.

Eight Bits

Since a bit can only be a zero or a one, it is not very useful if you wrote a letter to your friend and you want to save it to disk. There's only so much you can say by limiting your alphabet to two numbers. So computer engineers in the 1950s decided that they would group 8 bits together to represent each letter of the alphabet. There are 256 different combinations you can make with 8 zeros and ones, so it's more than enough to cover the alphabet and other special characters like the "?" and the "@". These 8 bits grouped together are called a byte.

The capital letter "A" is stored on your computer as
The asterisk symbol "*" is stored on your computer as
The name "Clinton" would look like this (spare the jokes, please):
010000110110110001101001011011100111010001101111 01101110
This sequence of numbers comprises seven letters, so it takes up 7 bytes.

If you made a new text file, typed the text "The quick brown fox jumped over the lazy dog", saved it, and looked at how much disk space it took up, it would say 44 bytes. Count the letters and spaces in that sentence: you'll see that it handily adds up to 44! Convenient, huh?

Revenge of the Metric System, sort of

Since a byte can only hold a very small piece of information, we often think in terms of kilobytes, megabytes, and gigabytes. But what do these terms mean?

A kilobyte (KB) is normally defined as 1,000 bytes. Technically, however, that is not the case. Because of tricky mathematics, a kilobyte is actually defined as 1,024 bytes. Most people just ignore those extra 24 bytes, so don't worry too much about it.

An average word-processing document will consume about 100 kilobytes. The average web page on the Internet is about 40 kilobytes large.

A megabyte (MB) is defined as 1,000 kilobytes or 1,000,000 bytes. However, because of the math, it technically ends up being 1,024 kilobytes and 1,048,576 bytes. That;s it -- no more math!

While documents are usually measures in kilobytes, whole programs are measured in megabytes. A few years ago, programs like WordPerfect came in diskette format. Each 3 1/2 inch diskette holds 1.44 megabytes of information. Programs were smaller then, so you would only need a few diskettes to hold the whole thing.

These days, the size of programs have gotten out of hand. The latest version of Netscape consumes a whopping 20 megabytes! Office products like Microsoft Word are even worse, sometimes topping 50 megabytes!

The Burden of Information

The increasing size of programs has resulted in larger and cheaper hard drives. Hard drives used to be measured in megabytes -- my first computer in 1988 had a 30-megabyte hard drive! Nowadays, hard drives are measured in gigabytes. For those taking notes, a gigabyte is defined as 1,024 megabytes. The average hard drive in a new computer is about 8-gigabytes. By next year, expect that number to double, as it has for the past few years.

Computers are allowing people to store more information each year, and computer users are quickly filling even those expansive hard drives. A full CD of music contains about 670 megabytes of data. But we didn't stop there -- CDs are now passé, as we look to the future with DVDs. A single DVD disk holds 14 gigabytes of information! Before you know it, we'll be talking about terabytes: that's right -- 1,024 gigabytes!

Is it any wonder that we live in what's called the Information Age?

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