WINDOWS核心编程之进程(二)

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指引我们向前进

<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT size=4>2004年7月14日&nbsp; 晚20:30</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT size=4></FONT></SPAN>&nbsp;</P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff1493 size=4>1.进程的实例句柄</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">加载到进程地址空间的每个可执行文件或</SPAN><SPAN lang=EN>DLL</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">文件均被产生一个唯一的实例句柄，就是</SPAN><SPAN lang=EN>hinstExe</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">参数</SPAN><SPAN lang=EN>.</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">有些这个参数的类型为</SPAN><SPAN lang=EN>HMODULE</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类型，</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">注意</SPAN><SPAN lang=EN>:</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">这两个类型是完全相同的对象。原因在于</SPAN><SPAN lang=EN>16</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">位的</SPAN><SPAN lang=EN>Windows</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中，</SPAN><SPAN lang=EN>HMODULE</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和</SPAN><SPAN lang=EN>HINSTANCE</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">用于标识不同的东西。</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p><FONT size=4>&nbsp;</FONT></o:p></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">当你在</SPAN><SPAN lang=EN>vc</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的环境里的</SPAN><SPAN lang=EN>link</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">里</SPAN><SPAN lang=EN>category</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">选</SPAN><SPAN lang=EN>ouput</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">有个</SPAN><SPAN lang=EN>base ,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">这标识着可执行文件的映像加载到的基地址</SPAN><FONT color=#ff0000><SPAN lang=EN>.vc</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">链接程序使用的默认基地址是</SPAN><SPAN lang=EN>0x00400000,</SPAN></FONT><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff0000>这是最低地址</FONT>，如果指定应确保在</SPAN><SPAN lang=EN>0x00400000</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">或大于这个地址。</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><o:p><FONT size=4>&nbsp;</FONT></o:p></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">要得到这个地址的值可以用</SPAN><SPAN lang=EN>HMODULE GetModuleHandle(PCTSTR pszModule)</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函数处理。</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN lang=EN>pszModule</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">就是可执行文件或</SPAN><SPAN lang=EN>dll</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">文件的名字，返回就是加载到进程的基地址。如果设定此参数为</SPAN><SPAN lang=EN>NULL, </SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">返回的就是可执行文件的基地址了。</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">注意</SPAN><SPAN lang=EN>:</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">可执行文件映像的基地址与可执行文件的基地址的区别</SPAN><SPAN lang=EN>.</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT color=#ff0000><FONT size=4><SPAN lang=EN>GetModuleHandle</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函数的两个重要特性</SPAN></FONT></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT color=#ff0000><FONT size=4><SPAN lang=EN>1.</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如果调用进程不使用常用的对话框函数</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">那么调用</SPAN><SPAN lang=EN>GetModuleHandle</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">并为它传递</SPAN><SPAN lang=EN>:ComDlg<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:chmetcnv TCSC="0" NumberType="1" Negative="False" HasSpace="False" SourceValue="32" UnitName="&#8221;" w:st="on">32&#8221;</st1:chmetcnv></SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">后</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">就会返回</SPAN><SPAN lang=EN>NULL, </SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">尽管</SPAN><SPAN lang=EN>ComDlg32.dll</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">可能加载到了其它进程的地址空间</SPAN><SPAN lang=EN>.</SPAN></FONT></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT color=#ff0000><FONT size=4><SPAN lang=EN>2</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">．如果</SPAN><SPAN lang=EN>GetModuleHandle(NULL)</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在</SPAN><SPAN lang=EN>dll</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中调用，返回的也是可执行文件的基地址，而不是</SPAN><SPAN lang=EN>DLL</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">文件的基地址</SPAN><SPAN lang=EN>.</SPAN></FONT></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><o:p><FONT size=4>&nbsp;</FONT></o:p></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff1493 size=4>2.进程的命令行</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">要获得一个指向进程的完整命令行的指针</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">可以用</SPAN><SPAN lang=EN>GetCommandLine</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函数</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>GetCommandLine();</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函数返回一个指向包含完整命令行的缓存的指针</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">是个完整路径名</SPAN><SPAN lang=EN>.</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><o:p><FONT size=4>&nbsp;</FONT></o:p></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">再介绍个函数</SPAN><SPAN lang=EN><FONT color=#ff0000>CommandLineToArgv</FONT>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">它是将字符串分割成它的各个标记</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">比如</SPAN><SPAN lang=EN>argc,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">其返回一个字符串指针的数组</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>PWSTR CommandLineToArgv(PWSTR pszCmdLine, int* pNumArgs);</FONT></SPAN></P><SPAN lang=EN><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN lang=EN>pNumArgs</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">是整数地址</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">设置为命令行中参数的数目</SPAN><SPAN lang=EN>.</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN lang=EN>CommaneLineToArgv</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">负责在内部分配内存</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">应用程序不释放该内存</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">它是在进程运行终止时由</SPAN><SPAN lang=EN>os</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">来释放的</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如果子自已来释放</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">应用</SPAN><SPAN lang=EN>HeapFree</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函数</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><o:p><FONT size=4>&nbsp;</FONT></o:p></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff1493 size=4>3.进程的环境变量</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">每个进程都有一个与它相关的环境块</SPAN><SPAN lang=EN>.</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">环境块是进程的地址空间中分配的一个内存块</SPAN><SPAN lang=EN>.</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">每个环境块都包含一组字符串</SPAN><SPAN lang=EN>.</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT size=4>例如</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>VarName1 = VarValue1/0</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>VarName2 = VarValue2/0</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;.</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>/0</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT size=4>注意</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT size=4>例如</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>XYZ= Windows</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>ABC=Windows</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">虽然</SPAN><SPAN lang=EN>XYZ</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">与</SPAN><SPAN lang=EN>ABC</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">有相同的值，但二者是不同的</SPAN><SPAN lang=EN>.</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>XYZ =Home</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN><FONT size=4>XYZ=Work</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT size=4>也是不同的，中间的空格区别了它们

Win98的环境变量写在了autoexec.bat里

Win2000中环境变量的名在

HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/SessionManager/Environment里

值写在了

HKEY_CURRENT_USER/Environment

只有拥有管理员的身份才可能对其进行修改。

使用DWORD GetEnvironmentVariable(PCTSTR pszName, PTSTR pszValue, DWORD cchValue);可以确定某个环境变量是否存在以及它的值。

第一个参数为名称，第二个为存放变量值的缓存， 第三个参数为缓存的大小(用字符数来表示)。

BOOL SetEnvironmentVariable(PCTSTR pszName, PCTSTR pszValue)修改与添加,删除变量，如果不存在pszName这样的变量就添加一个新的变量，如何存在就修改为pszValue。如果pszValue为NULL,就删除此变量。

 

4.进程的亲缘性

进程中的线程可以在主计算机中的任何一个CPU上执行。但是一个进程的线程可能被强制在可用CPU的子集上运行，这就叫进程的亲缘性。

 

5.进程的错误模式

UINT SetErrorMode(UINT fuErrorMode);

表要加上

CreateProcess里有一个参数指定了这个，使子进程错误如何处理

进程的当前驱动器和目录

如果调用CreateFile打开一个文件（不设定路径），那么系统就在当前驱动器和目录中查找该文件。用DWORD GetCurrentDirectory(DWORD cchCurDir, PTSTR pszCurDIr)可以得到

用BOOL SetCurrentDirectory(PCTSTR pszCurDir); 可以指定路径。

 

6.进程的当前目录

系统对进程的当前驱动器与目录保持跟踪，但它不跟踪每个驱动器的当前目录。这种支持是通过进程的环境字符串来提供的。例如进程有下面的两个环境变量。

=C:=C:/Utility/Bin

=D:=D:/Program Files

上面表示，驱动器C的进程的当前目录是/Utility/Bin, D的是/Program Files;

如果调用一个函数，传递一个驱动器全名，但不是当前的驱动器，那么系统就查看进程的环境块，找出与指定驱动器名相关的变量。如果存在，系统将该变量的值用作当前驱动器。如果不存在，系统将假设指定驱动器的当前目录是它的根目录。

例如进程的当前目录是C:/Utility/Bin,但调用CreateFile打开D:ReadMe.txt, 那么系统查看环境变量=D.如果=D存在，系统就从D:/Program File目录打开该ReadMe.txt文件。如果=D不存在，系统将从驱动器D的根目录来打开ReadMe.txt。

 

待续...............