小白最近闲来无事，自学了一点metapost，主要用它来绘制拓扑图或流程图。小白最近在写自己从工作以来的所学，写成了一份PDF的电子文档（小白不太会使用MS Word）。小白又不想使用JPEG或PNG格式的图片作为插图，因为它们不是矢量的图形，放大后图形就显得不够美观。
好了，废话不多说了，直接来个例子吧，这个插图来自是小白上学时的一本书《操作系统教程》。附代码如下：
# cat GnuLinux.mp
verbatimtex
\documentclass[10pt]{article}
\usepackage{CJK}
\AtBeginDocument{\begin{CJK}{UTF8}{gbsn}}
\AtEndDocument{\end{CJK}}
\begin{document}
etex
input boxes;
% system variables
ahangle := 40;
% fig0 is linux virtual file system topo
outputtemplate := "vfs.mps";
beginfig(0);
boxit.a(btex 用户进程 etex);
boxit.b(btex 系统调用界面 etex);
boxit.c(btex VFS etex);
boxit.d(btex Ext3 etex);
boxit.e(btex Buffer Cache etex);
boxit.f(btex 设备驱动程序 etex);
boxit.g(btex 硬盘控制器 etex);
boxit.minix(btex Minix etex);
boxit.nfs(btex NFS etex);
boxit.sysv(btex Sysv etex);
boxit.direc(btex 目录cache etex);
boxit.inode(btex Inode cache etex);
boxit.hard(btex etex);
% Len is the box's length
% Hig is the box's hight
numeric Len;
numeric Hig;
Len := 65;
Hig := 14pt;
a.e - a.w = (Len,0); a.n - a.s = (0,Hig);
b.e - b.w = (Len,0); b.n - b.s = (0,Hig);
c.e - c.w = (Len,0); c.n - c.s = (0,Hig);
d.e - d.w = (35,0); d.n - d.s = (0,Hig);
minix.e - minix.w = (35,0); minix.n - minix.s = (0,Hig);
nfs.e - nfs.w = (35,0); nfs.n - nfs.s = (0,Hig);
sysv.e - sysv.w = (35,0); sysv.n - sysv.s = (0,Hig);
e.e - e.w = (Len,0); e.n - e.s = (0,Hig);
f.e - f.w = (Len,0); f.n - f.s = (0,Hig);
g.e - g.w = (Len,0); g.n - g.s = (0,Hig);
direc.e - direc.w = (Len,0); direc.n - direc.s = (0,Hig);
inode.e - inode.w = (Len,0); inode.n - inode.s = (0,Hig);
% Dis is the hight between the boxes
numeric Dis;
Dis := 20;
a.s - b.n = (0,30);
b.s - c.n = (0,Dis);
c.s - d.ne = (5,Dis);
d.se - e.n = (-5,Dis);
c.s - nfs.nw = (-5,Dis);
d.w - minix.e = (10,0);
sysv.w - nfs.e = (10,0);
e.s - f.n = (0,Dis);
f.s - g.n = (0,30);
c.w - direc.e = (Dis,0);
c.e - inode.w = (-Dis,0);
hard.c = g.c;
hard.e - hard.w = (100,0);
hard.n - hard.s = (0,34);
drawboxed(a,b,c,d,e,f,g,minix,nfs,sysv,direc,inode,hard);
% draw the connectors
drawarrow a.s -- b.n;
drawarrow b.s -- c.n;
drawarrow c.s -- minix.n;
drawarrow c.s -- d.n;
drawarrow c.s -- nfs.n;
drawarrow c.s -- sysv.n;
pair A[];
A[1] = 1/5[e.nw,e.ne];
A[2] = 2/5[e.nw,e.ne];
A[3] = 3/5[e.nw,e.ne];
A[4] = 4/5[e.nw,e.ne];
drawarrow minix.s -- A[1];
drawarrow d.s -- A[2];
drawarrow nfs.s -- A[3];
drawarrow sysv.s -- A[4];
drawarrow e.s -- f.n;
drawarrow f.s -- g.n;
drawarrow c.w -- direc.e;
drawarrow c.e -- inode.w;
% draw the outline
pair B[];
B[1] = direc.w - (5,-56);
B[2] = inode.e - (-5,-56);
B[3] = inode.e - (-5,119);
B[4] = direc.w - (5,119);
draw B[1] -- B[2] -- B[3] -- B[4] -- cycle dashed evenly;
label.rt(btex 硬件层 etex,hard.e);
label.rt(btex Linux内核层 etex,b.e+(15,0));
label.rt(btex 系统调用 etex,a.se+(15,-5));
endfig;
end
小白觉得这些代码有些臃肿，因为是刚学，所以小白也只能做到这样了。后续还需多加练习，才能写出比较紧凑、高效的代码。
如何编译呢，在windows或gnu/linux系统上（需要安装相关TeX），
# mpost -tex=latex GnuLinux 或 # mpost -tex=latex GnuLinux.mp # mptopdf vfs.mps
效果图为：
