SI Prefixes

• You probably learned these in science class but just in case.
• Wikipedia page
• We will care about
  • pico - tera at least.

  • Name	Symbol	Base 10
    tera	T	$10^{12}$
    giga	G	$10^9$
    mega	M	$10^6$
    kilo	k	$10^3$
    mili	m	$10^{-3}$
    micro	$\mu$	$10^{-6}$
    nano	n	$10^{-9}$
    pico	p	$10^{-12}$

  • exa, zetta, and possibly yotta are something you should be aware of.
  • Name something that is measured in each unit.
• In general, we like to keep numbers between 1 and 1000.
• I have a file that is 102,304,288 bytes.
  • Represent this in scientific notation: $1.02 \times 10^{11} \text{bytes}$
  • Since I want the value to be between 1 and 1,000, I will covert to $10^9$ bytes per 1 Gb.
  • $1.02 \times 10^{11} \text{bytes} \times \frac{1Gb}{10^9 \text{bytes}}$
  • $1.02 \times 10^{\cancel{11}2} \cancel{\text{bytes}} \times \frac{1Gb}{10^{\cancel{\text{9}}1}\cancel{\text{bytes}}}$ The 9 in the denominator should be crossed out
  • $1.02 \times 10^2 Gb = 102 Gb$
  • I know this sounds silly, you can just do this one in your head, but practice it for me please.
  • We could have converted this to .1Tb, but this is not normal.
• A note on binary prefixes.
  • Like, Santa, they do exist.
  • See This reference
  • Generally they are powers of 2 or 1024.

  • Value	2	Name	Symbol
    $1024$	$2^{10}$	kibi	Ki
    $1024^{2}$	$2^{20}$	mebi	Mi
    $1024^{6}$	$2^{30}$	gibi	Gi
    $1024^{9}$	$2^{40}$	tebi	Ti
    $1024^{12}$	$2^{50}$	pebi	Pi
    $1024^{15}$	$2^{60}$	exbi	Ei