--- pubs/books/ucbka/trunk/c_cis0/c_cis0.tex 2016/10/06 03:15:02 4 +++ pubs/books/ucbka/trunk/c_cis0/c_cis0.tex 2017/07/03 01:59:16 140 @@ -1,58 +1,58 @@ -%$Header: /home/dashley/cvsrep/e3ft_gpl01/e3ft_gpl01/dtaipubs/esrgubka/c_cis0/c_cis0.tex,v 1.3 2002/09/12 23:30:20 dtashley Exp $ - -\chapter[Solutions: \ccilzeroxrefcomma{}Chapter \ref{ccil0}] - {Solutions: \ccilzeroxrefcomma{}Chapter \ref{ccil0}, \ccilzerolongtitle{}} - -\label{ccis0} - -\vworkexercisechapterheader{} -\begin{vworkexercisesolution}{\ref{exe:ccil0:sexe0:01}} -We can show this result in two ways. The first way, based on bit patterns, is to note -that adding an $m$-bit number, $u$, to its one's complement will result in a bit pattern -containing all 1's, i.e. $\forall i$, $u_{[i]} = 1$. Adding 1 to this bit pattern will -always produce $\forall i$, $u_{[i]} = 0$ with a carry out. Since the order of addition -does not matter, this establishes that adding $u$ to $\sim{}u+1$ will produce 0, thus showing -that $u$ and $\sim{}u+1$ are additive inverses. This method, although valid, does not -establish that $u$ and $\sim{}u+1$ actually represent additive inverses. For example, if -$u=-2^{m-1}$, $u=\sim{}u+1$, and clearly a non-zero number cannot be an additive inverse of -itself. Thus, it would be more comforting to show this result in a way that demonstrates the -actual values of the integers represented. - -We present a second method now. Assume that $u \neq -2^{m-1}$, since -$-2^{m-1}$ cannot have an additive inverse in an $m$-bit signed integer. -If $u=0$, $\sim{}u+1=0$, so the relationship is clearly met. If $u<0$, then -$u_{[m-1]}=1$, and by -(\ccilzeroxrefhyphen\ref{eq:ccil0:sroi0:sros0:00}), - - -\end{vworkexercisesolution} -\vworkexercisechapterfooter - -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -\vfill -\noindent\begin{figure}[!b] -\noindent\rule[-0.25in]{\textwidth}{1pt} -\begin{tiny} -\begin{verbatim} -$RCSfile: c_cis0.tex,v $ -$Source: /home/dashley/cvsrep/e3ft_gpl01/e3ft_gpl01/dtaipubs/esrgubka/c_cis0/c_cis0.tex,v $ -$Revision: 1.3 $ -$Author: dtashley $ -$Date: 2002/09/12 23:30:20 $ -\end{verbatim} -\end{tiny} -\noindent\rule[0.25in]{\textwidth}{1pt} -\end{figure} -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -% $Log: c_cis0.tex,v $ -% Revision 1.3 2002/09/12 23:30:20 dtashley -% Safety checkin as changing machines. -% -% Revision 1.2 2002/08/26 17:57:03 dtashley -% Additional solutions chapter added. Precautionary checkin to be sure -% that I've captured all changes. -% -% Revision 1.1 2002/08/26 17:35:06 dtashley -% Initial checkin. -% -%End of file C_CIS0.TEX +%$Header$ + +\chapter[Solutions: \ccilzeroxrefcomma{}Chapter \ref{ccil0}] + {Solutions: \ccilzeroxrefcomma{}Chapter \ref{ccil0}, \ccilzerolongtitle{}} + +\label{ccis0} + +\vworkexercisechapterheader{} +\begin{vworkexercisesolution}{\ref{exe:ccil0:sexe0:01}} +We can show this result in two ways. The first way, based on bit patterns, is to note +that adding an $m$-bit number, $u$, to its one's complement will result in a bit pattern +containing all 1's, i.e. $\forall i$, $u_{[i]} = 1$. Adding 1 to this bit pattern will +always produce $\forall i$, $u_{[i]} = 0$ with a carry out. Since the order of addition +does not matter, this establishes that adding $u$ to $\sim{}u+1$ will produce 0, thus showing +that $u$ and $\sim{}u+1$ are additive inverses. This method, although valid, does not +establish that $u$ and $\sim{}u+1$ actually represent additive inverses. For example, if +$u=-2^{m-1}$, $u=\sim{}u+1$, and clearly a non-zero number cannot be an additive inverse of +itself. Thus, it would be more comforting to show this result in a way that demonstrates the +actual values of the integers represented. + +We present a second method now. Assume that $u \neq -2^{m-1}$, since +$-2^{m-1}$ cannot have an additive inverse in an $m$-bit signed integer. +If $u=0$, $\sim{}u+1=0$, so the relationship is clearly met. If $u<0$, then +$u_{[m-1]}=1$, and by +(\ccilzeroxrefhyphen\ref{eq:ccil0:sroi0:sros0:00}), + + +\end{vworkexercisesolution} +\vworkexercisechapterfooter + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\vfill +\noindent\begin{figure}[!b] +\noindent\rule[-0.25in]{\textwidth}{1pt} +\begin{tiny} +\begin{verbatim} +$RCSfile: c_cis0.tex,v $ +$Source: /home/dashley/cvsrep/e3ft_gpl01/e3ft_gpl01/dtaipubs/esrgubka/c_cis0/c_cis0.tex,v $ +$Revision: 1.3 $ +$Author: dtashley $ +$Date: 2002/09/12 23:30:20 $ +\end{verbatim} +\end{tiny} +\noindent\rule[0.25in]{\textwidth}{1pt} +\end{figure} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +% $Log: c_cis0.tex,v $ +% Revision 1.3 2002/09/12 23:30:20 dtashley +% Safety checkin as changing machines. +% +% Revision 1.2 2002/08/26 17:57:03 dtashley +% Additional solutions chapter added. Precautionary checkin to be sure +% that I've captured all changes. +% +% Revision 1.1 2002/08/26 17:35:06 dtashley +% Initial checkin. +% +%End of file C_CIS0.TEX