Win 95及NT的注冊數據庫(Registry)是系統中非常重要的組成部分。在Win32 API中有一組Reg函數來處理這些問題。其一般的讀寫過程如下：
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??? 1、使用RegOpenKeyEx或RegCreateKeyEx函數打開或創建一個鍵；
??? 2、如果上一步成功，使用RegQueryValueEx讀取子鍵的值，使用RegSetValueEx設置子鍵值，使用RegEnumKey獲得所有子鍵，使用RegDeleteKey刪除一個鍵；
??? 3、完成操作后使用RegCloseKey關閉鍵。
??? 下面這段程序打開HKEY_CURRENT_USER\Software\Zeal SoftStudio\AskPro FTP\LastTime鍵，然后讀取WOL子鍵的值。

??? HKEY hkey;
??? char sz[256];
??? DWORD dwtype, sl = 256;
????
??? RegOpenKeyEx(HKEY_CURRENT_USER,
??? "Software\\Zeal SoftStudio\\AskPro FTP\\LastTime",
??? NULL, KEY_ALL_ACCESS, &hkey);
??? RegQueryValueEx(hkey, "WOL", NULL, &dwtype, (LPBYTE)sz, &sl);
??? RegCloseKey(hkey);
??? MFC程序可以使用CRegKey類讀寫注冊表。VB中調用API的辦法可以參考QA000226 "如何訪問Windows系統注冊表"。

??? 打開注冊鍵
??? LONG RegOpenKeyEx( HKEY hKey,? // handle to open key

??? LPCTSTR lpSubKey,????????????? // address of name of subkey to open
??? DWORD ulOptions,?????????????? // reserved =0
??? REGSAM samDesired,???????????? // security access mask
??? PHKEY phkResult??????????????? // address of handle to open key
??? );

??? 例:
??? HKEY hd;
??? hd=HKEY_LOCAL_MACHINE;
??? char* Regkeyname="SoftWare\\Xy123\\Poker\\";
??? LONG a=RegOpenKeyEx(hd,Regkeyname,0,KEY_READ,&hd);?? //成功返回ERROR_SUCCESS,否則返回錯誤代碼
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??? 關閉注冊鍵
??? LONG RegCloseKey( HKEY hKey // handle to key to close );
例:
???? RegCloseKey(HKEY_LOCAL_MACHINE);
OR:? RegCloseKey(hd);
建立注冊鍵
LONG RegCreateKeyEx( HKEY hKey, // handle to an open key
????? LPCTSTR lpSubKey, // address of subkey name
????? DWORD Reserved, // reserved =0
????? LPTSTR lpClass, // address of class string
????? DWORD dwOptions, // special options flag
????? REGSAM samDesired, // desired security access

????? LPSECURITY_ATTRIBUTES lpSecurityAttributes, // address of key security???????? structure
????? PHKEY phkResult, // address of buffer for opened handle
????? LPDWORD lpdwDisposition // address of disposition value buffer );
例:
?? char *sclass="";? //類名指定為空
?? DWORD nbf=0;??? //接受返回值,指明是建立新鍵還是打開已有的鍵.(經試驗總是返回REG_OPENED_EXISTING_KEY.
?? LONG II=RegCreateKeyEx(hd,Regkeyname,0,sclass,REG_OPTION_NON_VOLATILE,
??????????????? KEY_READ|KEY_WRITE,NULL,&hd,&nbf);

//REG_OPTION_NON_VOLATILE 指明鍵永久保留.安全結構指明NULL,自動獲得一默認值
//成功返回ERROR_SUCCESS,否則返回錯誤代碼
枚舉鍵值
LONG RegEnumValue( HKEY hKey, // handle to key to query
????? DWORD dwIndex, // index of value to query
????? LPTSTR lpValueName, // address of buffer for value string
????? LPDWORD lpcbValueName, // address for size of value buffer
????? LPDWORD lpReserved, // reserved =NULL
????? LPDWORD lpType, // address of buffer for type code

????? LPBYTE lpData, // address of buffer for value data
????? LPDWORD lpcbData // address for size of data buffer);
例:
?? DWORD dinx=0;
?? char valuename[70];? //分配數值名稱緩沖區
?? strcpy(valuename,"DeskPattern");? //隨便指定哪個鍵值名
?? DWORD nsize=69;? //數值名稱緩沖區大小
?? DWORD k=REG_SZ;? //指明數據類型
?? unsigned char vari[70]; //分配數值緩沖區
?? DWORD ncbvari=69; //數值緩沖區大小
?? dinx=0; //從0開始

?? while((II=RegEnumValue(hd,dinx,valuename,&nsize,NULL,&k,vari,&ncbvari))
????????? != ERROR_NO_MORE_ITEMS)
?? {
?????? dinx++;//索引 +1,準備取下一個值
?????? nsize=69; //恢復原來大小
?????? ncbvari=69;
?? }
成功后返回值0,各變量返回后設置如下:
valuename=數值名稱,以0結尾;如 : DeskColor
nsize=數值名稱長度, 9
k=REG_SZ? DeskColor 的類型為 REG_SZ
vari=鍵值,32768 DeskColor="32768",
ncbvari=鍵值長度 REG_SZ包括結尾0,=6,
讀取鍵值
LONG RegQueryValueEx( HKEY hKey, // handle to key to query

?????? LPTSTR lpValueName, // address of name of value to query
?????? LPDWORD lpReserved, // reserved
?????? LPDWORD lpType, // address of buffer for value type
?????? LPBYTE lpData, // address of data buffer
?????? LPDWORD lpcbData // address of data buffer size );
例:
?? RegQueryValueEx(hd,valuename,NULL,&k,vari,&ncbvari);
變量定義及成功后各變量設置值同RegEnumValueEx
寫鍵值
LONG RegSetValueEx( HKEY hKey, // handle to key to set value for
?????? LPCTSTR lpValueName, // name of the value to set

?????? DWORD Reserved, // reserved
?????? DWORD dwType, // flag for value type
?????? CONST BYTE *lpData, // address of value data
?????? DWORD cbData // size of value data );
例:
?? strcpy(valuename,"Hello");
?? unsigned char vari[10];
?? DWORD k=REG_SZ;
?? strcpy((char*)vari,"1234567")
?? RegSetValueEx(hd,valuename,0,k,vari,7);
成功后在Poker下增加一個鍵值 Hello : REG_SZ : 1234567
寫整型變量：
int hi=8;
RegSetValueEx(pj,valuename,0,REG_BINARY,(unsigned char*)&hi,sizeof(int));

成功后在Poker下增加一個鍵值 Hello2 : REG_BINARY :08 00 00 00

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void AddEventSource()
{
??? HKEY hk;
??? DWORD dwData;
??? UCHAR szBuf[80];

??? // Add your source name as a subkey under the Application
??? // key in the EventLog registry key.

??? if (RegCreateKey(HKEY_LOCAL_MACHINE,
??????????? "SYSTEM\\CurrentControlSet\\Services\
??????????? \\EventLog\\Application\\SamplApp", &hk))
??????? ErrorExit("Could not create the registry key.");

??? // Set the name of the message file.

??? strcpy(szBuf, "%SystemRoot%\\System\\SamplApp.dll");

??? // Add the name to the EventMessageFile subkey.

??? if (RegSetValueEx(hk,???????????? // subkey handle
??????????? "EventMessageFile",?????? // value name
??????????? 0,??????????????????????? // must be zero
??????????? REG_EXPAND_SZ,??????????? // value type
??????????? (LPBYTE) szBuf,?????????? // pointer to value data
??????????? strlen(szBuf) + 1))?????? // length of value data

??????? ErrorExit("Could not set the event message file.");

??? // Set the supported event types in the TypesSupported subkey.

??? dwData = EVENTLOG_ERROR_TYPE | EVENTLOG_WARNING_TYPE |
??????? EVENTLOG_INFORMATION_TYPE;

??? if (RegSetValueEx(hk,????? // subkey handle
??????????? "TypesSupported",? // value name
??????????? 0,???????????????? // must be zero
??????????? REG_DWORD,???????? // value type
??????????? (LPBYTE) &dwData,? // pointer to value data

??????????? sizeof(DWORD)))??? // length of value data
??????? ErrorExit("Could not set the supported types.");

??? RegCloseKey(hk);
}

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以下代碼把注冊表自啟動shell的鍵值改寫為C:\DK1\ATM\HARP\ExAtmShell.exe:

???????? HKEY hkey;
LONG res;
DWORD datatype=REG_SZ;
unsigned char szvalue[_MAX_PATH];
strcpy((char*)szvalue,"C:\\DK1\\ATM\\HARP\\ExAtmShell.exe");

res =::RegOpenKeyEx(HKEY_LOCAL_MACHINE,
"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Winlogon\\", 0,
KEY_WRITE|KEY_READ, &hkey);

if(res!=ERROR_SUCCESS)
{
AfxMessageBox("aaa");
return;
}
res = ::RegSetValueEx(hkey, "Shell", 0, datatype, szvalue, strlen(LPCSTR(szvalue)));

RegCloseKey(hkey);
if(res==ERROR_SUCCESS)
::AfxMessageBox("你已經成功地將注冊表自啟動shell的鍵值設置為C:\\DK1\\ATM\\HARP\\ExAtmShell.exe");
else
::AfxMessageBox("設定失敗:目標位置不存在這樣的鍵!");