00000009.htm

水木社区 embeded 版精华区 下载

The&nbsp;text&nbsp;explains&nbsp;things&nbsp;in&nbsp;some&nbsp;detail&nbsp;that&nbsp;will&nbsp;permit&nbsp;the&nbsp;reader&nbsp;to&nbsp;&nbsp;<br />
understand&nbsp;how&nbsp;and&nbsp;why&nbsp;things&nbsp;work&nbsp;and&nbsp;tips&nbsp;as&nbsp;to&nbsp;why&nbsp;some&nbsp;things&nbsp;may&nbsp;&nbsp;<br />
not.&nbsp;<br />
&nbsp;<br />
Embedded&nbsp;Systems&nbsp;Building&nbsp;Blocks&nbsp;2ed&nbsp;by&nbsp;Jean&nbsp;J.&nbsp;Labrosse&nbsp;[Recommended]&nbsp;&nbsp;<br />
&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
A&nbsp;useful&nbsp;book,&nbsp;if&nbsp;you&nbsp;are&nbsp;using&nbsp;microC/OS-II&nbsp;and&nbsp;want&nbsp;a&nbsp;kick-start.&nbsp;<br />
&nbsp;<br />
Embedded&nbsp;Systems&nbsp;Design&nbsp;by&nbsp;Steve&nbsp;Heath&nbsp;[Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
This&nbsp;book&nbsp;was&nbsp;a&nbsp;breath&nbsp;of&nbsp;fresh&nbsp;air.&nbsp;It&nbsp;is&nbsp;written&nbsp;by&nbsp;a&nbsp;working&nbsp;&nbsp;<br />
industrial&nbsp;embedded&nbsp;systems&nbsp;engineer,&nbsp;not&nbsp;an&nbsp;academic&nbsp;writing&nbsp;for&nbsp;&nbsp;<br />
students&nbsp;or&nbsp;a&nbsp;book&nbsp;aimed&nbsp;at&nbsp;the&nbsp;hobby&nbsp;market.&nbsp;<br />
&nbsp;<br />
Embedded&nbsp;Systems&nbsp;Programming&nbsp;in&nbsp;C&nbsp;and&nbsp;Assembly&nbsp;by&nbsp;John&nbsp;Forest&nbsp;Brown&nbsp;&nbsp;<br />
[Recommended]&nbsp;&nbsp;<br />
Derek&nbsp;Graham&nbsp;writes:&nbsp;<br />
The&nbsp;book&nbsp;is&nbsp;well&nbsp;written,&nbsp;is&nbsp;easy&nbsp;to&nbsp;read&nbsp;and&nbsp;all&nbsp;the&nbsp;diagrams&nbsp;are&nbsp;clear&nbsp;<br />
&nbsp;and&nbsp;unambiguous.&nbsp;<br />
&nbsp;<br />
Front&nbsp;Panel&nbsp;-&nbsp;Designing&nbsp;Software&nbsp;for&nbsp;Embedded&nbsp;User&nbsp;Interface&nbsp;by&nbsp;Niall&nbsp;&nbsp;<br />
D&nbsp;Murphy&nbsp;[Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
...the&nbsp;information&nbsp;and&nbsp;strategy&nbsp;for&nbsp;designing&nbsp;your&nbsp;own&nbsp;effective&nbsp;front&nbsp;&nbsp;<br />
panel.&nbsp;<br />
&nbsp;<br />
Industrial&nbsp;Control&nbsp;Handbook&nbsp;3rd&nbsp;ed.&nbsp;by&nbsp;Andrew&nbsp;Parr&nbsp;[Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
If&nbsp;you&nbsp;are&nbsp;in&nbsp;industrial&nbsp;control&nbsp;your&nbsp;company&nbsp;probably&nbsp;has&nbsp;this&nbsp;book&nbsp;&nbsp;<br />
already.&nbsp;If&nbsp;it&nbsp;does&nbsp;not&nbsp;ask&nbsp;&quot;why&nbsp;not?&quot;&nbsp;<br />
&nbsp;<br />
MicroC/OS-II&nbsp;-&nbsp;The&nbsp;Real&nbsp;Time&nbsp;Kernel&nbsp;by&nbsp;Jean&nbsp;J&nbsp;Labrosse&nbsp;[Highly&nbsp;&nbsp;<br />
Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
I&nbsp;completely&nbsp;recommend&nbsp;this&nbsp;book&nbsp;for&nbsp;MicroC/OS-II&nbsp;users;&nbsp;it&nbsp;will&nbsp;&nbsp;<br />
become&nbsp;their&nbsp;bible.&nbsp;<br />
&nbsp;<br />
Microcontroller&nbsp;Projects&nbsp;in&nbsp;C&nbsp;for&nbsp;the&nbsp;8051&nbsp;by&nbsp;Dogan&nbsp;Ibrahin&nbsp;[Recommended&nbsp;<br />
&nbsp;with&nbsp;Reservations]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
Master&nbsp;these&nbsp;projects&nbsp;and&nbsp;you&nbsp;have&nbsp;the&nbsp;basic&nbsp;building&nbsp;blocks&nbsp;for&nbsp;most&nbsp;&nbsp;<br />
8051&nbsp;programs.&nbsp;<br />
&nbsp;<br />
Microprocessor&nbsp;Architectures&nbsp;by&nbsp;Steve&nbsp;Heath&nbsp;[Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
Students&nbsp;will&nbsp;undoubtedly&nbsp;find&nbsp;this&nbsp;book&nbsp;helpful.&nbsp;Lecturers&nbsp;should&nbsp;get&nbsp;a&nbsp;<br />
&nbsp;copy&nbsp;before&nbsp;their&nbsp;students&nbsp;do.&nbsp;Engineers&nbsp;working&nbsp;on&nbsp;Motorola&nbsp;designs&nbsp;&nbsp;<br />
will&nbsp;also&nbsp;find&nbsp;that&nbsp;it&nbsp;should&nbsp;enhance&nbsp;their&nbsp;work.&nbsp;Recommended&nbsp;for&nbsp;&nbsp;<br />
Motorola&nbsp;users.&nbsp;<br />
&nbsp;<br />
PIC&nbsp;Your&nbsp;Personal&nbsp;Introductory&nbsp;Course&nbsp;by&nbsp;John&nbsp;Morton&nbsp;[Highly&nbsp;&nbsp;<br />
Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
Students&nbsp;and&nbsp;hobbyists&nbsp;have&nbsp;a&nbsp;gift&nbsp;in&nbsp;this&nbsp;book!&nbsp;At&nbsp;this&nbsp;price&nbsp;I&nbsp;would&nbsp;&nbsp;<br />
not&nbsp;be&nbsp;surprised&nbsp;if&nbsp;Microchip&nbsp;start&nbsp;giving&nbsp;it&nbsp;away&nbsp;to&nbsp;students&nbsp;instead&nbsp;&nbsp;<br />
of&nbsp;the&nbsp;standard&nbsp;data&nbsp;CD!&nbsp;<br />
&nbsp;<br />
Programming&nbsp;Embedded&nbsp;Systems&nbsp;in&nbsp;C&nbsp;and&nbsp;C++&nbsp;by&nbsp;Michael&nbsp;Barr&nbsp;&nbsp;<br />
[Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
If&nbsp;you&nbsp;wish&nbsp;to&nbsp;get&nbsp;into&nbsp;embedded&nbsp;programming&nbsp;this&nbsp;is&nbsp;a&nbsp;good&nbsp;book.&nbsp;I&nbsp;like&nbsp;<br />
&nbsp;it&nbsp;and&nbsp;would&nbsp;recommend&nbsp;it&nbsp;to&nbsp;students,&nbsp;home&nbsp;users&nbsp;or&nbsp;software&nbsp;engineers&nbsp;<br />
&nbsp;moving&nbsp;to&nbsp;embedded&nbsp;work.&nbsp;<br />
&nbsp;<br />
Real&nbsp;Time&nbsp;Software&nbsp;Systems&nbsp;by&nbsp;J&nbsp;E&nbsp;Cooling&nbsp;[Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
A&nbsp;must&nbsp;for&nbsp;all&nbsp;software&nbsp;engineering&nbsp;students&nbsp;who&nbsp;need&nbsp;to&nbsp;learn&nbsp;a&nbsp;&nbsp;<br />
methodology&nbsp;and&nbsp;those&nbsp;at&nbsp;home&nbsp;who&nbsp;thought&nbsp;they&nbsp;could&nbsp;never&nbsp;afford&nbsp;a&nbsp;CASE&nbsp;<br />
&nbsp;tool.&nbsp;One&nbsp;book&nbsp;covers&nbsp;the&nbsp;lot.&nbsp;<br />
&nbsp;<br />
Real-Time&nbsp;UML&nbsp;(2ed)&nbsp;by&nbsp;Bruce&nbsp;Douglass&nbsp;[Highly&nbsp;Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
a&nbsp;sensible&nbsp;straightforward&nbsp;introduction&nbsp;to&nbsp;UML&nbsp;&nbsp;<br />
&nbsp;<br />
Software&nbsp;Design&nbsp;for&nbsp;Real&nbsp;Time&nbsp;Systems&nbsp;by&nbsp;J&nbsp;E&nbsp;Cooling&nbsp;[Highly&nbsp;&nbsp;<br />
Recommended]&nbsp;&nbsp;<br />
Chris&nbsp;Hills&nbsp;writes:&nbsp;<br />
I&nbsp;highly&nbsp;recommend&nbsp;this&nbsp;book&nbsp;to&nbsp;all&nbsp;embedded&nbsp;engineers.&nbsp;<br />
&nbsp;<br />
Please&nbsp;note&nbsp;that&nbsp;opinions&nbsp;are&nbsp;those&nbsp;of&nbsp;the&nbsp;individual&nbsp;reviewers.&nbsp;<br />
&nbsp;<br />
&nbsp;<br />
------------------------------------------------------------------------&nbsp;<br />
--------&nbsp;<br />
Embedded&nbsp;Systems&nbsp;by&nbsp;Chris&nbsp;Hills&nbsp;&nbsp;<br />
Those&nbsp;of&nbsp;you&nbsp;who&nbsp;still&nbsp;have&nbsp;the&nbsp;old&nbsp;ACCU&nbsp;handbook&nbsp;from&nbsp;the&nbsp;era&nbsp;when&nbsp;I&nbsp;&nbsp;<br />
was&nbsp;Hon&nbsp;Sec&nbsp;may&nbsp;note&nbsp;that&nbsp;my&nbsp;biography&nbsp;had&nbsp;the&nbsp;comment&nbsp;&quot;Biggest&nbsp;mistake:&nbsp;<br />
&nbsp;Telling&nbsp;the&nbsp;ACCU&nbsp;Chair&nbsp;person&nbsp;that&nbsp;I&nbsp;had&nbsp;a&nbsp;good&nbsp;idea...&quot;&nbsp;After&nbsp;making&nbsp;&nbsp;<br />
some&nbsp;suggestions&nbsp;to&nbsp;The&nbsp;Editor&nbsp;about&nbsp;some&nbsp;things&nbsp;I&nbsp;would&nbsp;like&nbsp;to&nbsp;see&nbsp;&nbsp;<br />
in&nbsp;C&nbsp;Vu&nbsp;I&nbsp;find&nbsp;myself&nbsp;agreeing&nbsp;to&nbsp;an&nbsp;Embedded&nbsp;Feature&nbsp;for&nbsp;C&nbsp;Vu!&nbsp;<br />
&nbsp;<br />
I&nbsp;did&nbsp;put&nbsp;out&nbsp;a&nbsp;request&nbsp;for&nbsp;some&nbsp;support&nbsp;but&nbsp;this&nbsp;fell&nbsp;of&nbsp;deaf&nbsp;ears.&nbsp;&nbsp;<br />
This&nbsp;is&nbsp;unusual&nbsp;as&nbsp;I&nbsp;am&nbsp;informed&nbsp;(by&nbsp;Adrian&nbsp;Gothard&nbsp;at&nbsp;his&nbsp;talk&nbsp;on&nbsp;&nbsp;<br />
Embedded&nbsp;Systems&nbsp;at&nbsp;the&nbsp;ACCU&nbsp;Forum&nbsp;in&nbsp;Oxford)&nbsp;that&nbsp;embedded&nbsp;systems&nbsp;&nbsp;<br />
out&nbsp;number&nbsp;desktop&nbsp;systems&nbsp;by&nbsp;10&nbsp;to&nbsp;1!&nbsp;<br />
&nbsp;<br />
However&nbsp;a&nbsp;lot&nbsp;of&nbsp;these&nbsp;are&nbsp;mass-market&nbsp;consumer&nbsp;products.&nbsp;For&nbsp;example&nbsp;&nbsp;<br />
a&nbsp;team&nbsp;of&nbsp;4&nbsp;SW&nbsp;Engineers&nbsp;might&nbsp;turn&nbsp;out&nbsp;4&nbsp;embedded&nbsp;systems&nbsp;in&nbsp;a&nbsp;year&nbsp;&nbsp;<br />
that&nbsp;go&nbsp;in&nbsp;a&nbsp;car&nbsp;that&nbsp;sells&nbsp;20,000.&nbsp;(80,000&nbsp;systems).&nbsp;Actually&nbsp;many&nbsp;cars&nbsp;<br />
&nbsp;have&nbsp;more&nbsp;than&nbsp;4&nbsp;systems.&nbsp;Then&nbsp;there&nbsp;are&nbsp;lifts&nbsp;and&nbsp;entry&nbsp;systems,&nbsp;&nbsp;<br />
microwave&nbsp;cookers&nbsp;and&nbsp;washing&nbsp;machines,&nbsp;aircraft,&nbsp;ships,&nbsp;robots&nbsp;&nbsp;<br />
(thousands&nbsp;of&nbsp;them&nbsp;that&nbsp;make&nbsp;cars,&nbsp;cookers,&nbsp;washing&nbsp;machines&nbsp;etc.)&nbsp;&nbsp;<br />
radios,&nbsp;telephones&nbsp;and&nbsp;mobile&nbsp;phones&nbsp;(and&nbsp;additionally&nbsp;the&nbsp;SIM&nbsp;card&nbsp;in&nbsp;a&nbsp;<br />
&nbsp;mobile&nbsp;is&nbsp;an&nbsp;embedded&nbsp;system&nbsp;with&nbsp;a&nbsp;CPU&nbsp;in&nbsp;it's&nbsp;own&nbsp;right!)&nbsp;The&nbsp;list&nbsp;&nbsp;<br />
goes&nbsp;on&nbsp;and&nbsp;on.&nbsp;<br />
&nbsp;<br />
So&nbsp;you&nbsp;can&nbsp;see&nbsp;how&nbsp;embedded&nbsp;systems&nbsp;might&nbsp;outnumber&nbsp;desktop&nbsp;systems.&nbsp;&nbsp;<br />
Then&nbsp;there&nbsp;is&nbsp;the&nbsp;philosophical&nbsp;problem&nbsp;that&nbsp;most&nbsp;desktop&nbsp;systems&nbsp;are&nbsp;&nbsp;<br />
likely&nbsp;to&nbsp;contain&nbsp;one&nbsp;or&nbsp;two&nbsp;embedded&nbsp;systems...&nbsp;<br />
&nbsp;<br />
What&nbsp;makes&nbsp;an&nbsp;embedded&nbsp;system&nbsp;different&nbsp;to&nbsp;a&nbsp;desktop&nbsp;system?&nbsp;Embedded&nbsp;&nbsp;<br />
systems&nbsp;are&nbsp;usually&nbsp;but&nbsp;not&nbsp;always&nbsp;dedicated&nbsp;to&nbsp;a&nbsp;single&nbsp;task,&nbsp;have&nbsp;task&nbsp;<br />
&nbsp;specific&nbsp;IO&nbsp;and&nbsp;often&nbsp;only&nbsp;expect&nbsp;to&nbsp;communicate&nbsp;with&nbsp;another&nbsp;computer.&nbsp;<br />
&nbsp;Screens&nbsp;and&nbsp;[full&nbsp;QWERTY]&nbsp;keyboards&nbsp;are&nbsp;uncommon.&nbsp;The&nbsp;&quot;software&quot;&nbsp;is&nbsp;&nbsp;<br />
often&nbsp;burnt&nbsp;in&nbsp;to&nbsp;an&nbsp;EPROM&nbsp;or&nbsp;PROM&nbsp;(and&nbsp;then&nbsp;called&nbsp;firmware)&nbsp;this&nbsp;makes&nbsp;<br />
&nbsp;code&nbsp;patches&nbsp;difficult&nbsp;and&nbsp;in&nbsp;some&nbsp;cases&nbsp;impossible.&nbsp;The&nbsp;systems&nbsp;tend&nbsp;&nbsp;<br />
to&nbsp;have&nbsp;a&nbsp;minimum&nbsp;amount&nbsp;of&nbsp;memory&nbsp;and&nbsp;the&nbsp;8bit&nbsp;CPU&nbsp;still&nbsp;rules.&nbsp;&nbsp;<br />
&nbsp;<br />
Whilst&nbsp;some&nbsp;of&nbsp;the&nbsp;chips&nbsp;become&nbsp;dated&nbsp;as&nbsp;the&nbsp;leading&nbsp;edge&nbsp;moves&nbsp;on&nbsp;the&nbsp;&nbsp;<br />
embedded&nbsp;world&nbsp;is&nbsp;the&nbsp;opposite&nbsp;of&nbsp;the&nbsp;desktop.&nbsp;One&nbsp;does&nbsp;not&nbsp;write&nbsp;SW&nbsp;&nbsp;<br />
that&nbsp;will&nbsp;run&nbsp;on&nbsp;machines&nbsp;that&nbsp;are&nbsp;leading&nbsp;edge&nbsp;today&nbsp;and&nbsp;common&nbsp;&nbsp;<br />
tomorrow.&nbsp;One&nbsp;has&nbsp;to&nbsp;use&nbsp;a&nbsp;CPU&nbsp;that&nbsp;is&nbsp;cost&nbsp;effective&nbsp;in&nbsp;100,000&nbsp;off&nbsp;&nbsp;<br />
quantities&nbsp;today&nbsp;and&nbsp;in&nbsp;those&nbsp;quantities&nbsp;a&nbsp;10p&nbsp;($0.16)&nbsp;saved&nbsp;per&nbsp;CPU&nbsp;&nbsp;<br />
by&nbsp;using&nbsp;an&nbsp;older&nbsp;model&nbsp;is&nbsp;?0,000&nbsp;($16,000)&nbsp;in&nbsp;production.&nbsp;As&nbsp;the&nbsp;desk&nbsp;&nbsp;<br />
top&nbsp;runs&nbsp;headlong&nbsp;to&nbsp;64,&nbsp;128...&nbsp;bit&nbsp;processing&nbsp;and&nbsp;beyond&nbsp;the&nbsp;majority&nbsp;&nbsp;<br />
of&nbsp;the&nbsp;embedded&nbsp;world&nbsp;is&nbsp;still&nbsp;using&nbsp;8-16&nbsp;bit&nbsp;(and&nbsp;4&nbsp;bit&nbsp;is&nbsp;not&nbsp;&nbsp;<br />
completely&nbsp;dead)&nbsp;32&nbsp;bit&nbsp;is&nbsp;only&nbsp;the&nbsp;high&nbsp;end&nbsp;though&nbsp;the&nbsp;proliferation&nbsp;of&nbsp;<br />
&nbsp;the&nbsp;i86&nbsp;chips&nbsp;and&nbsp;(PC&nbsp;based)&nbsp;tools&nbsp;has&nbsp;brought&nbsp;their&nbsp;cost&nbsp;down.&nbsp;<br />
&nbsp;<br />
Lastly&nbsp;embedded&nbsp;systems&nbsp;are&nbsp;expected&nbsp;not&nbsp;to&nbsp;crash&nbsp;and&nbsp;if&nbsp;they&nbsp;do,&nbsp;to&nbsp;get&nbsp;<br />
&nbsp;themselves&nbsp;out&nbsp;of&nbsp;the&nbsp;jam.&nbsp;What's&nbsp;more&nbsp;they&nbsp;are&nbsp;expected&nbsp;to&nbsp;be&nbsp;&nbsp;<br />
fail-safe.&nbsp;I&nbsp;understand&nbsp;that&nbsp;Microsoft&nbsp;is&nbsp;planning&nbsp;to&nbsp;do&nbsp;an&nbsp;embedded&nbsp;&nbsp;<br />
version&nbsp;of&nbsp;Windows...&nbsp;You&nbsp;can&nbsp;try&nbsp;Ctl-Alt-Del&nbsp;in&nbsp;the&nbsp;lift&nbsp;next&nbsp;time&nbsp;it&nbsp;&nbsp;<br />
stops!&nbsp;<br />
&nbsp;<br />
There&nbsp;is&nbsp;also&nbsp;another&nbsp;difference&nbsp;between&nbsp;&quot;normal&quot;&nbsp;and&nbsp;embedded&nbsp;systems&nbsp;&nbsp;<br />
is&nbsp;that&nbsp;the&nbsp;tools&nbsp;tend&nbsp;to&nbsp;be&nbsp;a&nbsp;lot&nbsp;more&nbsp;expensive&nbsp;and&nbsp;specialised.&nbsp;One&nbsp;&nbsp;<br />
Borland&nbsp;compiler&nbsp;will&nbsp;run&nbsp;on&nbsp;virtually&nbsp;any&nbsp;PC&nbsp;produce&nbsp;software&nbsp;for&nbsp;&nbsp;<br />
almost&nbsp;any&nbsp;PC.&nbsp;Embedded&nbsp;tools&nbsp;run&nbsp;on&nbsp;a&nbsp;host&nbsp;that&nbsp;is&nbsp;separate&nbsp;to&nbsp;the&nbsp;&nbsp;<br />
target.&nbsp;The&nbsp;targets&nbsp;tend&nbsp;to&nbsp;be&nbsp;unique&nbsp;and&nbsp;may&nbsp;or&nbsp;may&nbsp;not&nbsp;run&nbsp;an&nbsp;&nbsp;<br />
operating&nbsp;system.&nbsp;The&nbsp;tools&nbsp;are&nbsp;usually&nbsp;tied&nbsp;to&nbsp;a&nbsp;specific&nbsp;CPU&nbsp;family;&nbsp;&nbsp;<br />
occasionally&nbsp;a&nbsp;specific&nbsp;CPU&nbsp;in&nbsp;that&nbsp;family.&nbsp;Whilst&nbsp;there&nbsp;may&nbsp;be&nbsp;millions&nbsp;<br />
&nbsp;of&nbsp;embedded&nbsp;systems&nbsp;there&nbsp;may&nbsp;be&nbsp;only&nbsp;a&nbsp;few&nbsp;developers&nbsp;for&nbsp;each&nbsp;tool.&nbsp;&nbsp;<br />
The&nbsp;80,000&nbsp;systems&nbsp;in&nbsp;the&nbsp;car&nbsp;cited&nbsp;earlier&nbsp;only&nbsp;had&nbsp;4&nbsp;developers&nbsp;who&nbsp;&nbsp;<br />
may&nbsp;only&nbsp;have&nbsp;had&nbsp;4&nbsp;compilers&nbsp;and&nbsp;one&nbsp;ICE.&nbsp;&nbsp;<br />
&nbsp;<br />
&nbsp;<br />
&nbsp;<br />
&nbsp;<br />
--&nbsp;<br />
执子之手，与子偕老。&nbsp;<br />
&nbsp;<br />
&nbsp;<br />
※&nbsp;来源:·BBS&nbsp;水木清华站&nbsp;smth.edu.cn·[FROM:&nbsp;166.111.218.77]&nbsp;<br />
<a href="00000009.htm">上一篇</a>
<a href="javascript:history.go(-1)">返回上一页</a>
<a href="index.htm">回到目录</a>
<a href="#top">回到页首</a>
</center>
<center><h1>BBS 水木清华站∶精华区</h1></center>
</body></html>