Page 329 - DCAP103_Principle of operating system

Principles of Operating Systems

Notes binary number, and a symbolic link to a directory or entry elsewhere in the registry. Symbolic
names are completely analogous to symbolic links in file systems or shortcuts on the Windows
desktop: they allow one entry to point to another entry or directory. A symbolic link can also
be used as a key, meaning that something that appears to be a directory is just a pointer to a
different directory.
Figure 10.5: The root keys registry keys and selected subkeys. The capitalization
has no meaning but follows the Microsoft practice here

Key Description
HKEY_LOCAL_MACHINE Properties of the hardware and software
HARDWARE Hardware description and mapping of hardware to
drivers

SAM Security and account information for users
SECURITY System-wide security policies
Generic information about installed application
SOFTWARE
programs
SYSTEM Information for booting the system
HKEY_USERS Information about the users; one subkey per user
USER_AST_ID User AST’s profile
AppEvents Which sound to make when (incoming email/fax,
error, etc.)
Console Command prompt settings (colours, fonts, history, etc.)

Control Panel Desktop appearance, screensaver, mouse ensitivity, etc.

Environment Environment variables
Keyboard Layout Which keyboard: 102-key US, AZERTY, Dvorak, etc.
Printers Information about installed printers

Software User preferences for Microsoft and third party software
HKEY_PERFORMANCE_DATA Hundreds of counters monitoring system performance
HKEY_CLASSES_ROOT Link to HKEY_LOCAL_MACHINE\SOFTWARE
CLASSES
HKEY_CURRENT_CONFIG Link to the current hardware profile

HKEY_CURRENT_USER Link to the current user profile

At the top level, the Windows 2000 registry has six keys, called root keys, as listed in Figure
10.5. Some interesting sub keys (subdirectories) are also shown here. To see this list on your
system, use one of the registry editors, either regedit or regedt32, which unfortunately display
different information and use different formats. They can also change registry values. Amateurs
should not change the keys or values on any system they plan to boot again. Just looking is
safe, though. You have been warned.
The first key (i.e., directory), HKEY_LOCAL_MACHINE, is probably the most important as it
contains all the information about the local system. It has five subkeys (i.e., subdirectories). The
HARDWARE subkey contains many subkeys telling all about the hardware and which driver
controls which piece of hardware. This information is displayed on the fly by the plug-and-play
manager as the system boots. Unlike the other subkeys, it is not stored on disk.

322 LOVELY PROFESSIONAL UNIVERSITY