The example registry entries in this chapter represent only the hierarchical relationship of the keys. For more information about the registry and registry file formats, see the documentation included in the Win32 SDK.
Windows provides a special repository called the registry that serves as a central configuration database for user-, application-, and computer-specific information. Although the registry is not intended for direct user access, the information placed in it affects your appli- cation's user interface. Registered information determines the icons, commands, and other features displayed for files. The registry also makes it easier to manage and support configuration information used by your application and eliminates redundant information stored in different locations.
The registry is a hierarchical structure. Each node in the tree is called a key. Each key can contain subkeys and data entries called values. Key names cannot include a space, backslash (\), or wildcard character (* or ?). In the HKEY_CLASSES_ROOT key, names beginning with a period (.) are reserved for special syntax (filename extensions), but you can include a period within a key name. The name of a subkey must be unique with respect to its parent key. Key names are not localized into other languages, although their values may be.
Note
The example registry entries in this chapter represent only the hierarchical relationship of the keys. For more information about the registry and registry file formats, see the documentation included in the Win32 SDK.
A key can have any number of values. A value entry has three parts: the name of the value, its data type, and the value itself. Value entries larger than 2048 bytes should be stored as files with their filenames stored in the registry.
When the user installs your application, register keys for where application data is stored, for filename extensions, icons, shell commands, OLE registration data, and for any special extensions. To register your application's information, you can create a registration file and use the Registry Editor to merge this file into the system registry. You can also use other utilities that support this function, or use the system-supplied registry functions to access or manipulate registry data.
Note
To use memory most efficiently, the system stores only the registry entries that have been installed and that are required for operation. Applications should never fail to write a registry entry because it is not already installed. To ensure this happens, use registry creation functions when adding an entry.