attachment:IpCheckSum.tex of IpCheckSum

   1 \documentclass[]{article}
   2 
   3 %opening
   4 \title{Ip Checksum Example}
   5 \author{Scot Anderson, Ph.D.}
   6 
   7 \begin{document}
   8 
   9 \maketitle
  10 
  11 \section{Example}
  12 
  13 \begin{tabular}{rrrrrr}
  14 	&  & $0001$ & $0001$ &  & $(17)$ \\
  15 	$+$ &  & $1111$ & $0111$ &  & $(-8)$ \\ \cline{1-4}\cline{6-6}
  16 	& $1$ & $0000$ & $1000$ &  &  \\
  17 	&  & \multicolumn{1}{l}{$\hookrightarrow $} & $+1$ &  &  \\ \cline{3-4}
  18 	&  & $0000$ & $1001$ & $=$ & $(9)$ \\
  19 	\multicolumn{6}{l}{Hence the checksum is:} \\
  20 	&  & $1111$ & $0110$ &  &
  21 \end{tabular}
  22 
  23 \bigskip
  24 
  25 If we sum up the original two numbers with the checksum we get:
  26 
  27 \begin{tabular}{rrrr}
  28 	&  & $0001$ & $0001$ \\
  29 	&  & $1111$ & $0111$ \\
  30 	$+$ &  & $1111$ & $0110$ \\ \cline{1-4}
  31 	&  & $11111$ & $1110$%
  32 \end{tabular}
  33 			
  34 Of courxse with the carry over we have:\ $1111~1111$ which is $-0.$ 
  35 
  36 \end{document}