WINDOWS核心編程之進程(二)

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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff1493 size=4>1.進程的實例句柄</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">加載到進程地址空間的每個可執行文件或</SPAN><SPAN lang=EN>DLL</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">文件均被產生一個唯一的實例句柄，就是</SPAN><SPAN lang=EN>hinstExe</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">參數</SPAN><SPAN lang=EN>.</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">有些這個參數的類型爲</SPAN><SPAN lang=EN>HMODULE</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">類型，</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">這兩個類型是完全相同的對象。原因在於</SPAN><SPAN lang=EN>16</SPAN><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; 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: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">用於標識不同的東西。</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">當你在</SPAN><SPAN lang=EN>vc</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的環境裏的</SPAN><SPAN lang=EN>link</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">裏</SPAN><SPAN lang=EN>category</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">選</SPAN><SPAN lang=EN>ouput</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">有個</SPAN><SPAN lang=EN>base ,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">這標識着可執行文件的映像加載到的基地址</SPAN><FONT color=#ff0000><SPAN lang=EN>.vc</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">鏈接程序使用的默認基地址是</SPAN><SPAN lang=EN>0x00400000,</SPAN></FONT><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff0000>這是最低地址</FONT>，如果指定應確保在</SPAN><SPAN lang=EN>0x00400000</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">或大於這個地址。</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">要得到這個地址的值可以用</SPAN><SPAN lang=EN>HMODULE GetModuleHandle(PCTSTR pszModule)</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函數處理。</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN lang=EN>pszModule</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">就是可執行文件或</SPAN><SPAN lang=EN>dll</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">文件的名字，返回就是加載到進程的基地址。如果設定此參數爲</SPAN><SPAN lang=EN>NULL, </SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">返回的就是可執行文件的基地址了。</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">可執行文件映像的基地址與可執行文件的基地址的區別</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函數的兩個重要特性</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如果調用進程不使用常用的對話框函數</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">那麼調用</SPAN><SPAN lang=EN>GetModuleHandle</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">併爲它傳遞</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">後</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">就會返回</SPAN><SPAN lang=EN>NULL, </SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">儘管</SPAN><SPAN lang=EN>ComDlg32.dll</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">可能加載到了其它進程的地址空間</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: 宋體; 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: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中調用，返回的也是可執行文件的基地址，而不是</SPAN><SPAN lang=EN>DLL</SPAN><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff1493 size=4>2.進程的命令行</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">要獲得一個指向進程的完整命令行的指針</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函數</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函數返回一個指向包含完整命令行的緩存的指針</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">是個完整路徑名</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">再介紹個函數</SPAN><SPAN lang=EN><FONT color=#ff0000>CommandLineToArgv</FONT>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">它是將字符串分割成它的各個標記</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">其返回一個字符串指針的數組</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">是整數地址</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">設置爲命令行中參數的數目</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">負責在內部分配內存</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">應用程序不釋放該內存</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">它是在進程運行終止時由</SPAN><SPAN lang=EN>os</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">來釋放的</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如果子自已來釋放</SPAN><SPAN lang=EN>,</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">應用</SPAN><SPAN lang=EN>HeapFree</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函數</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT color=#ff1493 size=4>3.進程的環境變量</FONT></SPAN></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=4><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">每個進程都有一個與它相關的環境塊</SPAN><SPAN lang=EN>.</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">環境塊是進程的地址空間中分配的一個內存塊</SPAN><SPAN lang=EN>.</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">每個環境塊都包含一組字符串</SPAN><SPAN lang=EN>.</SPAN></FONT></P><P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; 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: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">雖然</SPAN><SPAN lang=EN>XYZ</SPAN><SPAN style="FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">與</SPAN><SPAN lang=EN>ABC</SPAN><SPAN style="FONT-FAMILY: 宋體; 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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><FONT size=4>也是不同的，中間的空格區別了它們

Win98的環境變量寫在了autoexec.bat裏

Win2000中環境變量的名在

HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/SessionManager/Environment裏

值寫在了

HKEY_CURRENT_USER/Environment

只有擁有管理員的身份纔可能對其進行修改。

使用DWORD GetEnvironmentVariable(PCTSTR pszName, PTSTR pszValue, DWORD cchValue);可以確定某個環境變量是否存在以及它的值。

第一個參數爲名稱，第二個爲存放變量值的緩存， 第三個參數爲緩存的大小(用字符數來表示)。

BOOL SetEnvironmentVariable(PCTSTR pszName, PCTSTR pszValue)修改與添加,刪除變量，如果不存在pszName這樣的變量就添加一個新的變量，如何存在就修改爲pszValue。如果pszValue爲NULL,就刪除此變量。

 

4.進程的親緣性

進程中的線程可以在主計算機中的任何一個CPU上執行。但是一個進程的線程可能被強制在可用CPU的子集上運行，這就叫進程的親緣性。

 

5.進程的錯誤模式

UINT SetErrorMode(UINT fuErrorMode);

表要加上

CreateProcess裏有一個參數指定了這個，使子進程錯誤如何處理

進程的當前驅動器和目錄

如果調用CreateFile打開一個文件（不設定路徑），那麼系統就在當前驅動器和目錄中查找該文件。用DWORD GetCurrentDirectory(DWORD cchCurDir, PTSTR pszCurDIr)可以得到

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

 

6.進程的當前目錄

系統對進程的當前驅動器與目錄保持跟蹤，但它不跟蹤每個驅動器的當前目錄。這種支持是通過進程的環境字符串來提供的。例如進程有下面的兩個環境變量。

=C:=C:/Utility/Bin

=D:=D:/Program Files

上面表示，驅動器C的進程的當前目錄是/Utility/Bin, D的是/Program Files;

如果調用一個函數，傳遞一個驅動器全名，但不是當前的驅動器，那麼系統就查看進程的環境塊，找出與指定驅動器名相關的變量。如果存在，系統將該變量的值用作當前驅動器。如果不存在，系統將假設指定驅動器的當前目錄是它的根目錄。

例如進程的當前目錄是C:/Utility/Bin,但調用CreateFile打開D:ReadMe.txt, 那麼系統查看環境變量=D.如果=D存在，系統就從D:/Program File目錄打開該ReadMe.txt文件。如果=D不存在，系統將從驅動器D的根目錄來打開ReadMe.txt。

 

待續...............