The line `HKEY hKey;` in code is a declaration of...

The line HKEY hKey; in code is a declaration of a variable named hKey of type HKEY.

Explanation:

• HKEY is a data type in the Windows API, specifically in the context of the Windows Registry. It is used to represent a handle (a reference or pointer) to a key in the Windows Registry.
• This declaration does not actually do anything on its own; it simply creates the variable hKey to be used later in the program. Typically, such a variable is used in conjunction with registry-related Windows API functions like RegOpenKeyEx, RegCreateKeyEx, RegSetValueEx, etc., to open, create, read from, or modify a registry key.

For example, a typical usage might look like:

HKEY hKey;
if (RegOpenKeyEx(HKEY_CURRENT_USER, TEXT("Software\\MyApp"), 0, KEY_READ, &hKey) == ERROR_SUCCESS) {
    // Successfully opened the key
    // Do something with the key...
    RegCloseKey(hKey);
}

In this context:

• hKey is used to store the handle to a registry key.
• The program interacts with the registry using this handle.

Summary: HKEY hKey; just declares a registry key handle, preparing it for later use in Windows API calls.