Windows Registry Key

The Windows Registry was first introduced in Windows 3.1. At first, its primary goal was to save the configuration settings for COM (Component object module). These COM objects help the operating system to communicate among the process to share resources to avoid dead lock situation.When Windows 95 and NT were introduced, the usage of Windows Registry was extended by adding a new file format called .INI. This file format consists of simple text files with two categories sections and properties.

The Windows Registry keys contain keys and values. The keys contain the overall structure of a particular program like folders. The values are the non-container objects like files inside a folder. Whenever a process is called by the operating system, first it will check the root keys. The set of root keys is maintained by the Windows operating system. These root keys are Windows handle pointing to Windows Registry keys and it is case insensitive.

The hierarchy of the registry keys can be handled only by using a root key handle. Windows has 8 predefined unique root keys to map registry services. They are HKLM, HKCC, HKCR, HKCU, HKPD and HDD. Out of these keys, HKCC and HDD are available only in Windows 9X and NT type operating systems. Apart from root keys, there are Hives. These hives can be accessed only if its own root key handle initiates access. This is for ensuring security. Software program activation uses this kind of keys.

• HKLM – Hkey_local_machine
• HKCC –  Hkey_current_config
• HKCR –  Hkey_classes_root
• HKCU –  Hkey_current_user
• HKU –  Hkey_users
• HKPD –  Hkey_performance_data
• HKDD –  Hkey_dynamic_data

 Whenever a software program is installed in Windows a set of Windows Registry keys are created. These keys are called every time by the root keys when the program is on process. Even after uninstalling the software program, some registry keys still exists but inactive.

The Windows Registry is responsible for the correct access of requested .dll files. It is like a map given to the operating system to reach and make use of the correct .dll files. Because of that, even a small mistake in Windows Registry files and keys can result in permanent Windows operating system corruption.

The file formats used by Windows registry process are .INI, .Reg, .txt etc.  To edit the Windows Registry keys we need a registry editor. The default registry editor provided along with the Windows is regedit.exe. It allows user to make changes in the registry. But some most needed OS related registry keys are unavailable for user to modify.