Understanding Bits and Bytes

Learn about bits, bytes, megabits, megabytes and more.
Published: Jan 30, 2006
Author: Michael E, Callahan

This question submitted by Judith Ashelle, Bob Thompson, Andy Gibson, Donna Webster, Ann Metcalf and numerous others.

There's often confusion about all of the terms that stem from the words bits and bytes. Part of the problem stems from the fact that most of us are used to the decimal system, whereas computers utilize binary numbers. How is that a problem? Well, let's start at the beginning.

A bit is the smallest, most simple unit of information. The term "bit" comes from combining the words "binary digit." A bit is either a 1 or a 0. Another way to think of it is on or off. This on or off concept is used in many things in electronics, but we won't get into that right now. You don't tend to find bits wandering around by themselves. Instead they tend to collect in groups of eight which equals a byte. One character, like the letter z is a byte, or 8 bits.

If you think about it you'll find that factors of 8 appear in many different ways in computers. A 32-bit processor is 4 x 8 while a 64-bit processor is 8 x 8. You don't go out and by RAM in bunches of 100 megabytes. It's always a number divisible by 8�64, 128, 256, 512, and so on.

Under the decimal system the word "kilo" means one-thousand (1,000), but under the binary system it means one-thousand twenty-four (1,024). If you say your computer has 640K of RAM that means 640 kilobytes which is not 640,000 bytes, but rather 655,360 bytes. In dealing with computers you have to remember to multiply by 1,024, not by 1,000. In our society people have taken to using "K" to stand for 1,000, like "I paid 5K for that truck." Actually, "5K" would be 5,120.

Both disk space and memory are defined, ultimately, by the number of bytes available. A megabyte is roughly a million bytes while a gigabyte is roughly a billion bytes. I say "roughly" because if you remember that a "K" is really 1,024, then a true, accurate gigabyte would be 1,073,741,824 bytes. So, your 40 gigabyte hard drive really has more that 40 billion bytes.

The amount of data on the average computer is really quite staggering. I remember when the first 1.44 megabyte floppy disks came out. They could hold about 1.4 million bytes and that's about oh, 2,900 pages of text. Pages! Look at a 160 gigabyte hard drive and you're talking some serious storage. There was a time when I had every program I needed to work and they all occupied less than 12 megabytes. Today, just the copies of registered shareware programs that I keep on my computer is over 2 gigabytes. Amazing.

Lets sum this up a bit (no pun intended)

  • 1 bit - a 1 or a 0
  • 8 bits = 1 byte
  • 1,024 bytes = 1 kilobyte
  • 1,048,576 bytes = 1 megabyte
  • 1,073,741,824 bytes = 1 gigabyte

You also hear about bits and bytes in relation to transfer speeds. For example, you'll see modems will state what they can transfer in bits per second or bps. You'll also see references to Kbps or kilobytes per second and Mbps which is megabits per second. T1 lines are generally around 1.5 Mbps. Remember though that a megabit is not a megabyte. Some people get confused by the distinction. Just remember the difference between bits and bytes.

It takes 8 bits to equal 1 byte. By the same token, it takes 8 megabits to equal 1 megabyte. So, if you had a modem that could transfer 1 Mbps, it would be transferring 131,072 bytes per second, or 128 kilobytes per second. As long as you always remember the difference between bits and bytes, you should be fine.

I'd like to thank Judith Ashelle, Bob Thompson, Andy Gibson, Donna Webster, Ann Metcalf and numerous others for asking this question.

If you have a question on any technology topic that you'd like someone to tell you about you can submit it via e-mail by clicking HERE. You will not receive a reply, but all topics will be considered.

About Michael E, Callahan

Michael E. Callahan, known around the world by the trademarked name Dr. File Finder, is regarded as the world's leading expert on shareware. Dr. File Finder works with software programs and developers full-time, and in the average year he evaluates 10,000 programs. Since 1982 he has evaluated over 250,000 software and hardware products. Mr. Callahan began evaluating software online in 1982 and no one has been at it longer. He currently works doing online PR and marketing for software companies, and is the Senior Content Producer for Butterscotch.Com.

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