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\noindent Here are some terminologies relating to computing hardware, etc.


\section{Metric prefixes}

Some of these prefix names may be familiar, but here we give more
extensive listings than most people are familiar with and even more
than are likely to appear in typical computer science usage.  The
range in which typical usages occur is from Peta down to nano or pico.

A further note is that the terminologies are classicly used for powers
of 10, but most quantities in computer science are measured in terms
of powers of 2.  Since $2^{10}=1024$, which is close to $10^3$, computer
scientists typically use these prefixes to represent the nearby powers
of 2, at least with reference to big things like bytes of memory.

For big things:
   \begin{quote}
   \begin{tabular}{ccccc}
   Power & In CS, & Place-value & Metric & metric \\
   of 10 & may be & name        & prefix & abbrev. \\ \hline
   $10^{3}$  & $2^{10}$ & thousands    & kilo  & k \\
   $10^{6}$  & $2^{20}$ & millions     & mega  & M \\
   $10^{9}$  & $2^{30}$ & billions     & giga  & G \\
   $10^{12}$ & $2^{40}$ & trillions    & tera  & T \\
   $10^{15}$ & $2^{50}$ & quadrillions & peta  & P \\
   $10^{18}$ & $2^{60}$ & quintillions & exa   & E \\
   $10^{21}$ & $2^{70}$ & sextillions  & zeta  & Z \\
   $10^{24}$ & $2^{80}$ & septillions  & yotta & Y
   \end{tabular}
   \end{quote}

For small things:
   \begin{quote}
   \begin{tabular}{ccccc}
   Power & In CS, & Place-value & Metric   & metric \\
   of 10 & may be & name        & prefix   & abbrev. \\ \hline
   $10^{-3}$  & $2^{-10}$ & thousandths    & milli & m \\
   $10^{-6}$  & $2^{-20}$ & millionths     & micro & $\mu$ \\
   $10^{-9}$  & $2^{-30}$ & billionths     & nano  & n \\
   $10^{-12}$ & $2^{-40}$ & trillionths    & pico  & p \\
   $10^{-15}$ & $2^{-50}$ & quadrillionths & femto & f \\
   $10^{-18}$ & $2^{-60}$ & quintillionths & atto  & a \\
   $10^{-21}$ & $2^{-70}$ & sextillionths  & zepto & z \\
   $10^{-24}$ & $2^{-80}$ & septillionths  & yocto & y
   \end{tabular}
   \end{quote}


\section{Bits, bytes, nibbles, and pixels}

Information in computers is essentially stored as sequences of 0's and
1's.  For numbers, this is referred to as a {\em binary} or {base two}
representation, whereas our usual number system is base ten.  We will
learn more about binary numbers later, but for now, we just want to be
aware that numbers can be represented with the two digits 0 and 1 in
base two rather than the digits 0 through 9 that we use in base ten.

The term {\em bit} refers to one binary digit, i.e., a 0 or a 1.
Since a bit can have just two values, it is enough to represent one
small piece of information, e.g., a ``yes'' or ``no'' to some
question.  Typically, bits are organized into larger chunks that
encode more information.  For example, 8 bits are enough to represent
the numbers from 0 to 255.  A collection of 8 bits is referred to as a
{\em byte}.  Occasionally, computer scientists also like to refer to
chunks of 4 bits; the term for this is a {\em nibble}.

Bits may be abbreviated as ``b'' and bytes as ``B''; for example
``6GB'' would mean six gigabytes (see metric prefixes below).

The term ``pixel'' comes from ``picture element''.  It is a single
tiny dot on a computer monitor.  Color displays, generally specify an
amount of red, an amount of green, and an amount of blue for each
pixel, with the amount of each color expressed as a number from 0 to
255.  The range from 0 to 255 is exactly what can be represented with
one byte.  (Again, we will learn more later about representing numbers
in binary, but the 256 values we want to represent can be done with
one byte, because there are 8 bits in a bit, and $256=2^8$.)

Based on our discussion so far, we can see that 3 bytes of storage are
required to represent one pixel.  So if you have, for example, a 2
megapixel camera, the pictures it takes will require 6 megabytes if
stored in a naive fashion.  In reality, the storage requirement is
generally several times less than this, because pictures are typically
stored in a format such as JPEG that does image compression.  Instead
of just listing the three color values for every pixel in the image,
more sophisticated coding techniques are used.  For example, if a
corner of the image containing 100 pixels is a background of a solid
color, we could just note the boundaries of that region and that all
the pixels are of the same color instead of listing that color 100
times.  JPEG images are actually only an approximation of the original
picture, but it is generally possible to reduce the storage
requirement greatly without doing anything that the human eye will
notice.


\section{Other terms you may see in computer ads}

A limited selection is included here.

\begin{itemize}
 \item {\bf OS:} Operating System
 \item {\bf HD:} High definition (in reference to monitors)
 \item {\bf RAM:} Random-access memory.  Refers to the working memory
in the computer that primarlily determines the speed with which you
can run complex applications manipulating a lot of data.  Often, you
will see specific varieties mentionend such as SDRAM (xynchronous
dyanamic), DDR (double data rate), etc.
 \item {\bf MHz:} Megahertz (i.e., millions of cycles per second).
You may see this as a rating of how fast the memory or the central
processor can operate.  Usually, a higher clock rate means being able
to do things more quickly, but it is not an extremely reliable
indicator; it just measures the frequency of executing elementary
steps, but some processors utilize less powerful elementary operations
than others.
 \item {\bf RPM:} Revolutions per minute.  Along with the number of
bytes of storage, this is the other main measure for disk drives.  The
RPM gives some idea of how fast information can be read/written on the
disk drive.  (Some drives may also make reference to a RAID level,
which refers to a method of using multiple disks for increased speed
and/or redundancy (backup).)
 \item {\bf USB:} Universal serial bus.  The most common mechanism for
connecting peripherals like cameras and phones to your computer.
There are different versions, e.g., 2.0, 3.0, each allowing for faster
data transfers if both the computer and peripheral support it.
 \end{itemize}


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