Where did Kilo, Mega, Giga and all those other prefixes come from..?
They have entered our language. Everyone uses them. The terms, particularly with "byte", are almost commonplace. By convention multiples greater than one should be specified with a capital letter and those less that one with a lower case. Thus "Km" is correct but "km" is not.
The terms and their mathematical values
are: (for those that "tend to infinity")
|Deca||10^1||10||Greek meaning ten.|
|Hecta||10^2||100||Greek meaning hundred.|
|Kilo||1000^1||10^3||1,000||From Greek khiloi meaning 1000.|
|Mega||1000^2||10^6||1,000,000||From the Greek mega meaning "great", as in Alexandros Megos (Alexander the Great).|
|Giga||1000^3||10^9||1,000,000,000||From Latin gigas meaning "giant". Generally accepted as the value called a "Standard billion" in preference to the "English Billion which is only one hundred million.|
|Tera||1000^4||10^12||1,000,000,000,000||A "Standard Trillion". From Greek teras meaning "monster".|
|Peta||1000^5||10^15||1,000,000,000,000,000||From Greek pente meaning five (for 1000^5 = 1000 raised to the power five). This term and the next were added in 1975 by the General Conference of Weights and Measures (CGMP).|
|Exa||1000^6||10^18||1,000,000,000,000,000,000||From Greek hex meaning six. Taking "Hexa" and making the "H" silent (France is the home of the CGMP) gives "Exa".|
|Zetta||1000^7||10^21||1,000,000,000,000,000,000,000||Not to be mistaken for Greek Zeta. Last letter of the Latin alphabet. This prefix and the next were added in 1990 by CGMP.|
|Yotta||1000^8||10^24||1,000,000,000,000,000,000,000,000||Penultimate letter of the Latin alphabet.|
|Bronto||1000^9||10^27||1,000,000,000,000,000,000,000,000,000||Just keep on getting bigger... From the greek for Thunder.|
And going in the other direction, we have the terminology and amounts for numbers that "tend to zero" less than 1 (unity) but never truly reaching 0 - although the amounts can be so tiny that they can mostly be considered zero for all but scientific reasons. Note the terms less than 1 are written with a lower case letter. So you might have 1Mb but it takes 20mSec to fill it. Because there is repetition in some of the letters, micro is represented by the Greek letter "µ" (mu, pronounced 'myoo') similar-looking and often written as English "u".
|deci||10^-1||0.1||One tenth part, 1/10.|
|centi||10^-2||0.01||One hunderdth part, 1/100.|
|milli||10^-3||0.001||One thousandth part, 1/1000.|
|micro||10^-6||0.000,001||One millionth part, 1/1,000,000.|
|nano||10^-9||0.000,000,001||One thousandth millionth (one standard billionth), 1/1,000,000,000.|
|pico||10^-12||0.000,000,000,001||One million, millionth part, 1/1,000,000,000,000.|
|femto||10^-15||0.000,000,000,000,001||One million billionth part, 1/1000,000,000,000,000.|
|atto||10^-18||0.000,000,000,000,000,001||One billion billionth part, 1/1000,000,000,000,000,000.|
|zepto||10^-21||0.000,000,000,000,000,000,001||One thousand billion billionth part, 1/1000,000,000,000,000,000,000.|
|yocto||0.000,000,000,000,000,000,000,001||One million billion billionth part, 1/1000,000,000,000,000,000,000,000.|
Some find it useful to view a direct comparison of the above - it provides perspective on the scales...
Approaching Infinity <--------------|--------------> Approaching Zero 0.000,000,000,000,000,000,000,001 yocto 10^-24 0.000,000,000,000,000,000,001 zepto 10^-21 0.000,000,000,000,000,001 atto 10^-18 0.000,000,000,000,001 femto 10^-15 0.000,000,000,001 pico 10^-12 0.000,000,001 nano 10^-9 0.000,001 micro 10^-6 0.001 milli 10^-3 0.01 centi 10^-2 0.1 deci 10^-1 1 Unity 10^0 10 Deca 10^1 100 Hecta 10^2 1,000 Kilo 10^3 1,000,000 Mega 10^6 1,000,000,000 Giga 10^9 1,000,000,000,000 Tera 10^12 1,000,000,000,000,000 Peta 10^15 1,000,000,000,000,000,000 Exa 10^18 1,000,000,000,000,000,000,000 Zetta 10^21 1,000,000,000,000,000,000,000,000 Yotta 10^24 1,000,000,000,000,000,000,000,000,000 Bronto 10^27
Many of the above grouping terms are bandied about with little regard to the sheer size of the number. Consider the following:
There are 86,400 seconds in one day. Assuming an average life span of 80 years, each of us has 2,522,880,000 seconds to live. Sounds quite a lot, but consider this: If you are middle-aged, you have around a billion seconds left to live. Can you hear ticking?
But what is that Billion in comparison?