Registry is a database repository for information about a computer's configuration. Registry contains information that Windows continually references during operation, such as:
Profiles for each user.
The programs installed on the computer and the types of documents each can create.
Property settings for folders and program icons.
What hardware exists on the system.
Which ports are being used.
Registry is organized hierarchically as a tree and is made up of
keys and their
subkeys,
hives and
value entries.
Registry Editor is available that enable you to inspect and modify registry. The navigation area of Registry Editor displays folders, each of which represents a predefined key on the local computer. When accessing registry of a remote computer, only two predefined keys, HKEY_USERS and HKEY_LOCAL_MACHINE, appear.
| Predefined Keys | Description |
| HKEY_CURRENT_USER (HKCU) | Contains the root of the configuration information for the user who is currently logged on. The user's folders, screen colors and Control Panel settings are stored here. This information is referred to as a user's profile. |
| HKEY_USERS (HKU) | Contains the root of all user profiles on the computer. HKCU is a subkey of HKU. |
| HKEY_LOCAL_MACHINE (HKLM) | Contains configuration information particular to the computer (for any user). |
| HKEY_CLASSES_ROOT (HKCR) | Is a subkey of HKLM\Software. The information stored here ensures that the correct program opens when you open a file by using Windows Explorer. |
| HKEY_CURRENT_CONFIG (HKCC) | Contains information about the hardware profile used by the local computer at system startup. |
The following table lists the data types currently defined and used by the system.
| Value Types | Description |
| Binary Value | Raw binary data. Most hardware component information is stored as binary data and is displayed in Registry Editor in hexadecimal format. |
| DWORD Value | Data represented by a number that is 4 bytes long. Many parameters for device drivers and services are this type and are displayed in Registry Editor in binary, hexadecimal or decimal format. |
| Expandable String Value | A variable-length data string. This data type includes variables that are resolved when a program or service uses the data. |
| Multi-String Value | A multiple string. Values that contain lists or multiple values in a form that people can read are usually this type. Entries are separated by spaces, commas or other marks. |
| String Value | A fixed-length text string. |