From Bits & Bytes to Yottabytes
A friend recently said she got confused about which was bigger: kilobytes, megabytes, gigabytes, etc.
Ah ha! An easy little article, I thought. A cheat sheet for newbies. I’ll just look up what comes after terabyte and whip a quick article together.
How wrong I was.
Megs & Gigs
The prefix part is pretty straightforward. The kilo, mega, giga, etc. comes from the standardized SI naming scheme. SI is the International System of Units (from the French Le Système International d’Unités) and was adopted in 1960. In the U.S. school systems it was often called the metric system.
| kilo | = 103 | = 1,000 |
| mega | = 106 | = 1,000,000 |
| giga | = 109 | = 1,000,000,000 |
| tera | = 1012 | = 1,000,000,000,000 |
| peta | = 1015 | = 1,000,000,000,000,000 |
| exa | = 1018 | = 1,000,000,000,000,000,000 |
| zetta | = 1021 | = 1,000,000,000,000,000,000,000 |
| yotta | = 1024 | = 1,000,000,000,000,000,000,000,000 |
The confusion comes when applying SI prefixes to computer measurements.
Bits & Bytes
The most basic piece of computer data is a bit. Think of it as a switch. It’s off or on. A zero or a one.
Obviously a single bit doesn’t give you a lot of data – on/off, yes/no, true/false. So they grouped bits together and called them bytes. It is theoretically possible to vary the number of bit per byte, but all personal computer on the market now use 8 bits per byte. Eight bits grouped together gives you 256 possible combinations – enough to code any character used in the West.
Kilobytes & Kibibytes
Because all those little switches have only two states – off or on – a lot of computer measurements are powers of 2. Base 2 if you remember your math.
At some point, someone decided that 210 equals 1024 and that is almost 1000 so let’s call it a kilobyte. And when we have 1024 kilobytes we’ll call if a megabyte, etc. on up the SI list.
And that is where the trouble started. The average user – like you and me – used the SI definitions. A kilo means 1000 – not 1024. Even computer manufacturers were confused – sometimes a megabyte was 1,000,000 bytes and sometimes it was 1,048,576 bytes. As the numbers got bigger so did the differences.
Confusion reigned and lawsuits were filed. “If you are going to call it a kilo, then it should be 1000. If you want to measure in 1024, then call it something else” said users.
So they did. They took the first two letters from the SI list and added bi (for binary) and byte.
| kibibyte | = 210 | = 1,024 |
| mebibyte | = 220 | = 1,048,576 |
| gibibyte | = 230 | = 1,073,741,824 |
| tebibyte | = 240 | = 1,099,511,627,776 |
| pebibyte | = 250 | = 1,125,899,906,842,624 |
| exbibyte | = 260 | = 1,152,921,504,606,846,976 |
| zebibyte | = 270 | = 1,180,591,620,717,411,303,424 |
| yobibyte | = 280 | = 1,208,925,819,614,629,174,706,176 |
The new naming scheme is still in the process of being adopted and standardized. Your computer may be measuring in kibibytes and still calling them kilobytes.
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