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Bits n' Bytes

Understanding Bits, Bytes, Megabytes, and Overbites

There are few things more confusing when it comes to computers than understanding the difference between bits, bytes, kilobytes, megabytes, gigabytes and modem speeds calibrated in bps or bits per second. So without further ado -- and at the risk of great personal humiliation -- here is the ultimate, definitive explanation of these cryptic terms.

Technically, the word "bit" is an acronym, short for Binary digIT, so if one were inclined to pick nits, the word "bit," in computer parlance, should always be written "BIT" -- in all capital letters. How's that for a bit of minutia?

A "bit" by definition is the smallest unit of data that a computer can recognize. It requires eight bits to make up one byte, and one byte equals one character, such as the letter "a" or the numeral "7." You might think of eight bits to the byte as you would eight ounces to the cup or eight quarts to the peck. It's simply the sum of the smaller units comprising a single, larger unit.

Modems quantify the amount of data they can transmit in terms of bps or bits-per-second, analogous to automobile speed being quantified in mph or miles-per-hour. So a 56kbps modem is capable of transmitting up to 56,000 bits per second.

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Okay, break out the slide rule, here's where it gets tricky:

We know that eight bits equals one byte, and one byte equals one character, so 56,000 bits (as in bits-per-second) divided by eight (eight bits to the byte) results in 7,000 bytes or characters transmitted per second. What you have read so far in this article is approximately 1,300 characters. So you can see that a 56kbps modem is capable of transmitting a substantial amount of data -- approximately twice the amount of text contained in this entire article -- every second.

A "kilobyte" is 1,000 bytes and is abbreviated K or KB -- not to be confused, which it often is, with a kilobit, which is abbreviated kb. So if things weren't confusing enough, 1,000KB and 1,000kb are not the same.

Going back to our 56kbps modem, the "kbps" translates to "thousand bits per second," so putting it all together, we have "56,000 bits-per-second." The "bps" is frequently omitted when discussing modems, so most modems are described as simply 56k. (To further complicate matters, the designated 56kbps modem speed is actually a theoretical data transmission rate attainable only under ideal laboratory conditions. In the real world, 56k modems transmit data at speeds somewhat less than 56k.)

When you look at a "Details" view of file names on your computer using Windows Explorer (Start > Programs > Windows Explorer > View > Details), under the "Size" column you'll see various numbers representing the size of each file. File sizes are expressed in KB or kilobytes, i.e. 74KB, 218KB, etc. You may occasionally see a number that's larger than 1,000, such as 1,714KB or 2,567KB. And that takes us to "megabytes."

A "megabyte" is 1 million bytes and is abbreviated MB. So if you see a file size that's 1,714KB, mentally add three zeros to the number so it becomes 1,714,000, and that's 1.7MB or 1.7 million bytes.

When you purchase RAM (memory) for your computer, that memory is available in units of 64MB or 128MB or 256MB -- megabytes. Older hard drives were also measured in megabytes, such as 500MB or 750MB of disk space. Personal computers in the early 1980s had no hard drives and relied on floppy disks to store data. When the first hard drives appeared on the digital scene, a 40MB hard drive was cause for waking the kids and calling the neighbors.

Moving along from megabytes, the next level up is "gigabytes." A gigabyte is 1,000 megabytes and is abbreviated GB. Ultra cool computer dudes and dudesses refer to gigabytes as "gigs," but we civilized folk refer to "gigabytes," thankyouverymuch.

Gigabytes are the largest quantification you're likely to encounter in the world of computerdom, though there are larger units of measure. For example, a "terabyte" is 1,000 gigabytes, and is abbreviated TB. In fact, there is an emerging technology bringing us a new product called a "Hyper CD-ROM" that can hold 10TB (roughly 10,000 gigabytes) of data. When is enough enough? That is the eternal question.

If a terabyte is cramping your style, you can move up to the petabyte, exabyte, zetabyte, yottabyte (all true!) and, of course, the orthodontist's favorite, the overbyte. Badda-bing, badda-boom.

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