301. LaTeX技巧358：用Latex画程序框图

\setlength{\unitlength}{1mm}
\newcommand{\wrt}[1]{\makebox(0,0)[c]{#1}}
\newcommand{\lline}[1]{\line(-1,0){#1}}
\newcommand{\rline}[1]{\line(1,0){#1}}
\newcommand{\uline}[1]{\line(0,1){#1}}
\newcommand{\dline}[1]{\line(0,-1){#1}}
\newcommand{\lvec}[1]{\vector(-1,0){#1}}
\newcommand{\rvec}[1]{\vector(1,0){#1}}
\newcommand{\uvec}[1]{\vector(0,1){#1}}
\newcommand{\dvec}[1]{\vector(0,-1){#1}}
\newsavebox{\condition}
\newsavebox{\process}
\newsavebox{\inputoutput}
\savebox{\process}(0,0){\thicklines
\put(-10,-3){\framebox(20,6){}}
}
\savebox{\condition}(0,0){\thicklines
\put(-10,0){\line(2,1){10}}
\put(-10,0){\line(2,-1){10}}
\put(10,0){\line(-2,1){10}}
\put(10,0){\line(-2,-1){10}}
}
\savebox{\inputoutput}(0,0){\thicklines
\put(-10.5,-3){\rline{18}}
\put(-10.5,-3){\line(1,2){3}}
\put(10.5,3){\lline{18}}
\put(10.5,3){\line(-1,-2){3}}
}
\begin{center}
\begin{picture}(45,73)(20,-73)\thicklines
\put(40,3){\oval(15,6)}\put(40,3){\wrt{开始}} \put(40,0){\dvec{5}}
\put(40,-8){\usebox{\inputoutput}} \put(40,-8){\wrt{输入$m,\,n$}}
\put(40,-11){\dvec{5}} \put(40,-19){\usebox{\process}}
\put(40,-19){\wrt{$i=1$}} \put(40,-22){\dvec{8}}
\put(40,-33){\usebox{\process}} \put(40,-33){\wrt{$a=m\times i$}}
\put(40,-36){\dvec{5}} \put(40,-46){\usebox{\condition}}
\put(40,-46){\wrt{$n$整除$a$?}} \put(40,-51){\dvec{5}}
\put(41,-53){\makebox(0,0)[l]{是}}
\put(40,-59){\usebox{\inputoutput}} \put(40,-59){\wrt{输出$a,\,i$}}
\put(40,-62){\dvec{5}}
\put(40,-70){\oval(15,6)}\put(40,-70){\wrt{结束}}
\put(30,-46){\line(-1,0){15}} \put(28,-45){\makebox(0,0)[b]{否}}
\put(15,-46){\uvec{10}} \put(15,-33){\usebox{\process}}
\put(15,-33){\wrt{$i=i+1$}} \put(15,-30){\line(0,1){5}}
\put(15,-25){\rvec{25}}

\end{picture}
\end{center}