The Windows Registry 8






Using the Registry: Program Examples


The following sample code demonstrates how to use the registry functions.


  1. Enumerating Registry Subkeys Program Example
  2. Creating the Registry Subkey and Value Program Example
  3. Deleting Registry Key with Subkeys Program Example
  4. Determining the Registry Size Program Example
  5. Querying the Registry Value Program Example


Enumerating Registry Subkeys Program Example


The following example uses the RegQueryInfoKey(), RegEnumKeyEx(), and RegEnumValue() functions to enumerate the subkeys of the specified key. The hKey parameter passed to each function is a handle to an open key. This key must be opened before the function call and closed afterward. Create a new empty Win32 console application project. Give a suitable project name and change the project location if needed.

Then, add the source file and give it a suitable name.

Next, add the following source code.


// QueryKey - Enumerates the subkeys of key and its associated values.

//     hKey - Key whose subkeys and values are to be enumerated.

#include <windows.h>

#include <stdio.h>


#define MAX_KEY_LENGTH 255

#define MAX_VALUE_NAME 16383


void QueryKey(HKEY hKey)


    WCHAR    achKey[MAX_KEY_LENGTH];   // buffer for subkey name

    DWORD    cbName;                   // size of name string

    WCHAR    achClass[MAX_PATH] = TEXT("");  // buffer for class name

    DWORD    cchClassName = MAX_PATH;  // size of class string

    DWORD    cSubKeys=0;               // number of subkeys

    DWORD    cbMaxSubKey;              // longest subkey size

    DWORD    cchMaxClass;              // longest class string

    DWORD    cValues;              // number of values for key

    DWORD    cchMaxValue;          // longest value name

    DWORD    cbMaxValueData;       // longest value data

    DWORD    cbSecurityDescriptor; // size of security descriptor

    FILETIME ftLastWriteTime;      // last write time


    DWORD i, retCode;


    WCHAR  achValue[MAX_VALUE_NAME];

    DWORD cchValue = MAX_VALUE_NAME;


    // Get the class name and the value count.

    retCode = RegQueryInfoKey(

        hKey,                    // key handle

        achClass,                // buffer for class name

        &cchClassName,           // size of class string

        NULL,                    // reserved

        &cSubKeys,               // number of subkeys

        &cbMaxSubKey,            // longest subkey size

        &cchMaxClass,            // longest class string

        &cValues,                // number of values for this key

        &cchMaxValue,            // longest value name

        &cbMaxValueData,         // longest value data

        &cbSecurityDescriptor,   // security descriptor

        &ftLastWriteTime);       // last write time


      wprintf(L"RegQueryInfoKey() returns %u\n", retCode);


    // Enumerate the subkeys, until RegEnumKeyEx() fails

    if (cSubKeys)


        wprintf(L"\nNumber of subkeys: %d\n", cSubKeys);


        for (i=0; i<cSubKeys; i++)


            cbName = MAX_KEY_LENGTH;

            retCode = RegEnumKeyEx(hKey, i,achKey,&cbName,NULL,NULL,NULL,&ftLastWriteTime);

            if (retCode == ERROR_SUCCESS)


                wprintf(L"(%d) %s\n", i+1, achKey);





            wprintf(L"No subkeys to be enumerated!\n");


    // Enumerate the key values

    if (cValues)


        wprintf(L"\nNumber of values: %d\n", cValues);           


        for (i=0, retCode=ERROR_SUCCESS; i<cValues; i++)


            cchValue = MAX_VALUE_NAME;

            achValue[0] = '\0';

            retCode = RegEnumValue(hKey, i, achValue, &cchValue, NULL, NULL, NULL, NULL);


            if (retCode == ERROR_SUCCESS)


                wprintf(L"(%d) %s\n", i+1, achValue);





            wprintf(L"No values to be enumerated!\n");



int wmain(int argc, WCHAR *argv[])


   HKEY hTestKey;


   // Change the key and subkey accordingly...

   // In this case: HKEY_USERS\\S-1-5-18\\...

   if(RegOpenKeyEx(HKEY_LOCAL_MACHINE,  L"SYSTEM\\Setup" /*L"S-1-5-18"*/,  0, KEY_READ,  &hTestKey) == ERROR_SUCCESS)

   // if(RegOpenKeyEx(HKEY_LOCAL_MACHINE,  L"SYSTEM\\WPA",  0, KEY_READ,  &hTestKey) == ERROR_SUCCESS)


         wprintf(L"RegOpenKeyEx() is OK! Registry key is HKEY_LOCAL_MACHINE\\SYSTEM\\Setup...\n");




         wprintf(L"RegOpenKeyEx() failed!\n");


   if(RegCloseKey(hTestKey) == ERROR_SUCCESS)

         wprintf(L"hTestKey key was closed successfully!\n");


         wprintf(L"Fail to close hTestKey key!\n");


   return 0;



Build and run the project. The following screenshot is a sample output.


Enumerating Registry Subkeys Program Example: A sample console program output in action


Verify the result against the real registry keys.


Enumerating Registry Subkeys Program Example: Verifying the program output through Windows registry





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