this is for holding javascript data
Michela Ceria edited bits1.tex
almost 8 years ago
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\section{Bits standard operations and logic}\index{LectNo1}
A \emph{bit} (binary digit) is a unit of measure for information, introduced
by C. Shannon in
1948. 1948.\\ Roughly speaking, it represents the minimal amount of
information needed in order to distinguish among
to events two events, occurring with the
same
probability. probability\\ Bits are used in Information Theory and - in general - in
most of Computer Science applications.
\\
They are represented with the constants $0 $ and $1$ (the two events with the
same probability). In Mathematics, the set of bits is usually denoted by
%We have the Field of Bits $\Fb$. When we work in Computer Science we often
%consider
%two fundamental constants: $0 $ and $1$. These, viewed as a set
\[
\Fb = \{0,1\}
\]
The first topic we need to
introduce introduce, in order to work with
bits bits, is
how we can perform operations with them, so how to equip the set $\Fb$ with two operations: sum and multiplication, in some sense analogous to the
possibility of performing usual operations with
them. numbers.
\\
In the following table, we can see how to sum and multiply bits.
%can be enriched with the standard operations ``$+$'' and ``$\cdot$'':
\begin{table}[!htb]
\centering
\begin{tabular}{c|c|c|c}
...
\caption{Sum and product}\label{SumProd}
\end{table}
The first
column and second
columns one, represent the values of
the two input variables $a$ and $b$,
used to represent the two bits we have to sum or to multiply; the third and the fourth
ones ones, respectively represent the results of the sum and
the product of $a$ and $b$.\\
\medskip
Performing operations with bits is not the same as doing so with ``usual''
(real) numbers (from now on, we denote the set of real numbers with $\RR$).
\\