CertiGuide to A+ (A+ 4 Real)  9  Chapter 1: What are Operating Systems and How Do They Work?       9  The Registry

The Registry 1 Registry Keys and Values

The benefit of the Registry is that it provides a centralized, standardized storage system for configuration options and application data, as opposed to the multiple files and file formats used in the DOS days. The registry is split into 5 “hives” that cover the four major parts of Windows; 6 “hives” in Windows ME¹⁹

This hive is present mainly for legacy application compatibility reasons, and contains file extension information; un-installation data and COM object details. From Windows 2000, this hive is actually a virtual hive that displays information merged from other locations. It is rare that manual changes are made to this hive.

This hive stores user specific configuration data for each user that has a profile on the computer. Configuration settings such as keyboard layout, language preferences, sounds and third party application settings are stored here on a per-user basis. This hive is effectively the storage mechanism that allows Windows to have separate configurations and preferences for each user. It is relatively uncommon to edit this hive directly; instead, logging on as a user and editing the HKEY_CURRENT_USER hive is the usual practice.

This hive is created when a user logs into Windows. It is actually a virtual reference to a key stored in HKEY_USERS associated with the currently logged on account. Creating a virtual hive in this manner allows applications to write information to the Registry easily – instead of having to determine the registry key associated with the current user, data written directly to this hive is guaranteed to be stored in the current user’s configuration keys. The contents of this hive are copied back to the appropriate key in the HKEY_USERS hive when the user logs off. Manually editing this hive is common, and a useful troubleshooting technique.

This hive stores two distinct types of data. Firstly, it stores application and Windows settings that apply to all users, much like a global version of the HKEY_USERS hive. Secondly, it stores information on all the hardware installed in the computer, and uses this information to manage the plug and play and resource allocation systems. Editing the application settings stored in this hive is a common troubleshooting technique. However, alter manually the hardware configuration is a risky task and should be used with great care.

In the same way, that HKEY_CURRENT_USER is a virtual reference to a key contained within HKEY_USERS; this hive is a virtual reference to HKEY_LOCAL_MACHINE. When Windows boots up, a hardware profile is copied to a special key under HKEY_LOCAL_MACHINE called “CurrentControlSet”. This key is then used for all hardware information storage and retrieval until the computer is rebooted or powered off. Hardware profiles and the CurrentControlSet key are discussed shortly.

The Registry 1 Registry Keys and Values