Bytes and bits - How to Size Up Computer Components and Internet Speeds
(updated 03/25/10)
by Randy Yates
One of the things people have the most trouble with, when first learning how to use a computer, is the complicated jargon. There are many terms associated with computers. Here, we hope to shed some light on things.
To start things off, lets talk about the metric way of grouping numbers. This is essential to understanding how many computer terms work. Americans are used to the imperial measuring system. We are about the only nation left in the world that uses it. Everyone else uses the metric system. The metric system is much more simple than the imperial system.
As an example, there are 12 inches in a foot, three feet in a yard, 5280 feet in a land mile and approximately 6076 feet in a nautical mile. There are 16 ounces in a pound, 8 ounces in a cup, 2 cups in a pint, 2 pints in a quart, and 4 quarts in gallon. That is the how the imperial system works. There's very little order and everything is sort of random. There are historic reasons for each of these units, but the historic reasons aren't really relative today.
Today, we could be much more efficient if we used the metric system. The standard unit of length in the metric system is the meter. Since a meter is around 3.28 feet, we can't measure small things with it. So we can divide that meter into smaller parts. We don't, however, divide it up into some obscure number of sections, as the imperial system does with feet and inches. Instead, we divide by ten. Ten is the magic number in the metric system. We use ten because, as humans, we prefer the decimal system. After all, we have ten fingers, so we count by tens. A creature with 16 fingers may count by sixteens.
A tenth of a meter is a decimeter. A tenth of a decimeter (one hundredth of a meter) is a centimeter. A tenth of a centimeter is a millimeter. These units keep getting divided by ten to form a new unit. Each has a new prefix to the word followed by "meter".
Now what about the other direction? A meter isn't very handy for representing large distances. Ten meters is a decameter. Ten decameters is a hectometer. Finally, ten hectometers is a kilometer. One thousand kilometers is a megameter. One thousand megameters is a gigameter. One thousand gigameters is a terameter. There are prefixes that go much higher and lower than the ones I've listed here so far. Here is a nice table showing metric prefixes.
Metric Prefix Table
| Prefix | Symbol | Multiplier | Exponential |
| yotta | Y | 1,000,000,000,000,000,000,000,000 | 1024 |
| zetta | Z | 1,000,000,000,000,000,000,000 | 1021 |
| exa | E | 1,000,000,000,000,000,000 | 1018 |
| peta | P | 1,000,000,000,000,000 | 1015 |
| tera | T | 1,000,000,000,000 | 1012 |
| giga | G | 1,000,000,000 | 109 |
| mega | M | 1,000,000 | 106 |
| kilo | k | 1,000 | 103 |
| hecto | h | 100 | 102 |
| deca | da | 10 | 101 |
| 1 | 100 | ||
| deci | d | 0.1 | 10¯1 |
| centi | c | 0.01 | 10¯2 |
| milli | m | 0.001 | 10¯3 |
| micro | µ | 0.000001 | 10¯6 |
| nano | n | 0.000000001 | 10¯9 |
| pico | p | 0.000000000001 | 10¯12 |
| femto | f | 0.000000000000001 | 10¯15 |
| atto | a | 0.000000000000000001 | 10¯18 |
| zepto | z | 0.000000000000000000001 | 10¯21 |
| yocto | y | 0.000000000000000000000001 | 10¯24 |
Now, let's talk about bits and bytes. Bits and bytes are bit more complicated than a natural metric scale represents. A bit is a word formed from the shortening of the words "binary digit". It is a single binary digit. This means that it can be 0 or 1. That's it. Binary is a counting system where a digit can be one of two (bi is the prefix meaning two) possible things. We use this in computers because circuits have only two possible states, on or off. In computers, 0 represents "off", while 1 represents "on". That's easy to follow isn't it?' We now know what a bit is.
The simple definition of a byte is that it is eight bits. To reduce some confusion, you can research further as to why it's eight bits. I'll just say that it's due to how a computer represents a character in binary. A character like the letter "A", is created from eight binary digits typically. In the past, bytes have been other sizes, but eight bits is the standard used today. Eight was preferred because it is a power of two which is important to the rest of this discussion.
It isn't necessary to learn binary in order to understand what different computer terms mean, but it is helpful to understand where it comes from. Two to the power of 10, is 1024. This many bytes is considered a kilobyte. A squared kilobyte, or 10242 is a megabyte. A megabyte is exactly 1,048,576 bytes. Many people round both of these numbers down to a number easier to remember. A kilobyte is roughly 1,000 bytes. A megabyte is roughly 1,000,000 bytes. The terms themselves are used to remember the estimated size, due to the metric scale.
So, based off our metric table from earlier, a billion bytes is a gigabyte. A trillion bytes is a terabyte. Bytes don't go into the negative exponential. So you wouldn't have a centibyte or a millibyte. DVD disks and computer hard drives can be measures in either way. Typically manufactures will use the measurement that makes their product sound the best. So if you buy a stack of DVD disks that claim to hold 4.7GB (gigabytes) each, they aren't lying, but the disk will actually only hold around 4,400 megabytes. The number is misleading because people expect to be able to put 4,700 megabytes on the disk.
Hopefully, all of this hasn't left you more confused than you were before. To understand what other crazy computer terms mean, first learn what the original unit is. For instance, pixels are dots. A pixel is a single point in an image. Dot pitch is the distance between pixels. DPI, or Dots per inch, is a measurement of resolution often used in printing. Screen resolutions are measured in pixels horizontal by vertical. Let's briefly look at each of these, and you'll soon be able to understand some terms better.
Pixels are dots. Since you are looking at a computer monitor, you are looking at millions of dots. If you look real close, you may be able to see them. You can definitely see them on an older CRT monitor. If you have an older CRT television, it's even easier to see them. A pixel is a unit of measurement that helps define the clarity of an image. The more pixels an image has, the better it will look. Of course this also depends on dot pitch and DPI. The lower the dot pitch, the higher the DPI. This is simply stating that when you have less space between pixels, you can fit more of them in a square inch.
So, when you buy a digital camera, one of the terms used to describe the camera is it's "megapixels". This is a description of how many pixels each image will contain. So, a camera that is described as 1.3 megapixels, contains roughly 1,300,000 pixels. This is actually found by the resolution units multiplied with each other. If you have a screen resolution on your computer monitor of 1280x1024 (SXGA resolution for fullscreen 4:3 monitors), it would be 1.3 megapixels. The "1280" is the number of pixels horizontally, while "1024" is vertical. The higher the megapixel rating a camera has, the better the pictures it produces will look. There are many other factors such as the type of lens and the quality of the camera to take into consideration, but we are focusing only on the terms here.
Perhaps that helps you understand what the term megapixel means. What about 720p and 1080p? What do those terms mean? They are used to refer to hi-def televisions and you probably know that 1080p is better than 720p, but where do they get those terms.
The answer goes straight back to pixels. A hi-def television that is advertised as 720p has a vertical screen resolution of 720 pixels. The "p" at the end doesn't stand for pixels, however, that means "progressive scan". Standard television resolution is 640x480, or 480i. The "i" means interlaced. Interlacing is used to fool your eyes. Most people could not tell the difference between 1080i and 1080p. The difference is that 1080i requires less picture processing, because each frame is only half of the picture. Every other line is blank. Then the next frame switches it up. Every other frame is rendered. Progressive scan doesn't do this. It renders every frame completely. 1080p is better than 1080i when it comes to clarity, but many people would not notice the difference.
Finally, let's talk about internet connections and broadband speeds. Typically an internet service provider (ISP) will sell different packages. They try to keep the technical details hidden from the casual user and describe the speeds in terms of how fast one can download a normal picture or video. ISPs usually have a "lite" package or tier.Then they'll have various other tier levels up to the "ultimate" tier. This is the highest speed they offer.
These tiers are actually based off of megabits per second. A typical ISP 1st Tier (lite) service may offer a one megabit download speed. These speeds wouldn't be confusing if they used "megabyte" instead of "megabit". One could see that a typical music file is around four megabytes and calculate how long it would take to download a normal music file. ISPs love to use the term megabit, however. This is partly due to the fact that 20 megabits sounds much better than 2.5 megabytes. As our DVD example points out, the larger numbers make the product appear to be better.
So, in order to find out the actual time it will take to download a music file that is four megabytes in size over a one megabit connection, first we will need to convert either megabytes to megabits or convert megabits to megabytes. In this particular case, it's easiest to convert the four megabytes file size over to bits. To do this, we multiply by eight. This would give us an estimated 32 megabits. Now, since we have a one megabit per second download speed, we can see that it would take around 32 seconds to get a four megabyte file. Of course, this is only if you actually getting a full one megabit per second transfer rate.
In conclusion, there are many terms that seem very confusion at first, but they are really not that bad once you learn the why and how of it all. I hope that this has helped some of you, and I also hope that it hasn't added to the confusion. If you are confused about any other terms, or if you have more tech-related questions for me, email me at:
ask.randy.yates [at] gmail.com
You'll want to replace the [at] with the @ symbol. I do that to reduce the chance that an email crawler will find my email address on the web and start sending it spam.