9.如何判断文件在磁盘上是否存在？\MainFrm.cpp
................................\MainFrm.h
................................\ReadMe.txt
................................\..lease\_desktop.ini
................................\res\Test.ico
................................\...\Test.manifest
................................\...\Test.rc2
................................\...\TestDoc.ico
................................\...\Toolbar.bmp
................................\...\_desktop.ini
................................\Resource.h
................................\stdafx.cpp
................................\stdafx.h
................................\Test.cpp
................................\Test.h
................................\Test.rc
................................\Test.sln
................................\Test.suo
................................\Test.vcproj
................................\TestDoc.cpp
................................\TestDoc.h
................................\TestView.h
................................\_desktop.ini
................................\UpgradeLog.XML
................................\Test.ncb
................................\_UpgradeReport_Files\UpgradeReport.css
................................\....................\UpgradeReport_Minus.gif
................................\....................\UpgradeReport_Plus.gif
................................\....................\UpgradeReport.xslt
................................\Test.aps
................................\TestView.cpp
................................\Test.vcproj.7E42065F1EA8492.Administrator.user
................................\Release
................................\res
................................\_UpgradeReport_Files
9.如何判断文件在磁盘上是否存在？