The Registry is a set of data files used to help Windows control hardware, software, the user's environment, and the "look and feel" of the Windows interface. Formerly, these functions were performed by WIN.INI, SYSTEM.INI, and .INI files that are associated with applications.
The evolution of application and operating system control has three distinct levels:
Originally, SYSTEM.INI and WIN.INI controlled all Windows and application features and access. It worked well when average users used only a few applications. As the number and complexity of applications grew, so did the number of entries to the .INI files. The downside of this approach, in a growing environment, is that everyone would make changes to the .INI files when applications were added to the system. However, no one ever removed references from their .INI files when they removed applications, so SYSTEM.INI and WIN.INI continued to get larger and larger. Each incremental size increase meant slower performance. Even upgrading applications presented its challenges. The upgrade would add entries but never take the old ones away, presumably to ensure compatibility if another program was to access the settings.
Because the maximum size of an .INI file is 64KB, an obvious problem arose. To counter the problem, vendors started supplying .INI files of their own, with just pointers to the specific .INI files in WIN.INI and SYSTEM.INI. The downside of this approach was the proliferation of .INI files throughout the system and the hierarchical nature of access. (If WIN.INI made a particular setting, and an application's .INI file overrode that setting, who was responsible and where should--or could--a system-wide setting that had priority be made?)
Another potential problem arose because of the .INI files. Because any user could easily edit the files with any text editor, the .INI files were always at risk. Users could try to edit the files and make mistakes, which might make the files useless, and the applications that they controlled non-functional. Also, there could also be a security problem because of the ease of access to the files and the information they contained.
The Registry is a set of files that control all aspects of the operating system and how it works with outside events. Those "events" range from accessing a hardware device directly to how the interface will react to a specific user to how an application will be run and much more. It was designed to work exclusively with 32-bit applications, and file size is limited to a whopping 40MB. That should be sufficient for most users, and usually the ones who do have a problem with it are only those with a very large number of users on an NT network. It would be nearly impossible to fill 40MB of Registry with application information alone. (Whenever you say some-thing "is more than we'll ever need," just remember that IBM said that about the meager 16KB of RAM on the original IBM PC). Because Windows 95 networking is peer-to-peer, each system controls only itself, and has no Registry information on other systems. A Windows NT system may hold user information on thousands of people, dramatically increasing the Registry size.
Fortunately, if more space is required for the Registry because of the number of users, the network can be split up into multiple domains.
The Registry is complex by its very nature, and on purpose.
The Registry is the data file for all 32-bit hardware/driver combinations and 32-bit applications in both Windows NT and Windows 95. Sixteen-bit drivers do not work in NT, so all devices are controlled through the Registry, even those normally controlled by the BIOS. In Windows 95, 16-bit drivers will continue to work as real-mode devices, and they use SYSTEM.INI for control.
Sixteen-bit applications will work in either NT or 95, and the applications still refer to WIN.INI and SYSTEM.INI files for information and control.
Without the Registry, the operating system would not have the necessary information to run, to control attached devices, to launch and control applications, and to respond correctly to user input.
The Registry is a database of all the settings and locations of 32-bit drivers
in the system. Figure 1.1 illustrates the positioning of the Registry in relation
to Windows NT and the drivers.
Figure 1.1.
Windows uses the Registry to control hardware.
When the OS needs to access hardware devices, it uses drivers,
even if the device
is a BIOS-supported device.
With Windows NT, the appropriate drivers are loaded, based on the information the BIOS supplies to NT. From that point on, NT never looks to the BIOS for information again, unless the system is restarted. Windows 95 also utilizes drivers for BIOS-supported devices, but continues to interact with the BIOS for some items.
NOTE: The utilization of BIOS information in Windows 95 allows greater backward compatibility with hardware than is available with Windows NT. Windows 95 has the capability to use both older and newer hardware than is usable with Windows NT, because new drivers are easier to write for 95, and 95 can still use real-mode drivers. This makes 95 more flexible than NT on the one hand, and more unstable on the other.
Non-BIOS-supported devices that are installed must also have a driver. The drivers are independent of the OS, but the OS needs to know where to find them, the filename, the version, and other settings and information. Depending on the device, the driver may be different for NT and 95. Some devices, like modems, use exactly the same drivers for both NT 4.0 and Windows 95. Without Registry entries for each of the devices, they would not be usable. Likewise, any problems with the Registry may also make them unusable. Obviously, if a programmer makes a mistake in the setup files that affect the Registry settings, the device may not work at all.
SOLUTIONS: If I have a bad driver, how can I get a new one? If the driver you have is not working correctly, first try reinstalling the driver from the original disk. If the device still doesn't work, get a new driver from the manufacturer. Many times, the driver that ships with a device will be prepared before the final touches are made to the product. Inevitably, there will then be differences that may make the driver incompatible, or it may contain a bug. The best place today to get a new driver from a manufacturer is to download it from the company's Internet Web site. Usually, the device documentation will contain the address to the site, and you can then download the driver directly. Another alternative is to download it from the manufacturer's technical bulletin board (BBS) directly. Again, many manufacturers put a number in the documentation. If you have no addresses available to get the file directly, call the technical support phone number and ask for a new driver. Most of the time, they will ask you for the date or version number of the driver, which you can get from the Control Panel, Windows NT Diagnostics, or other utilities such as Norton Utilities.
When a user attempts to launch an application, the Registry supplies application
information to the OS so the application can be found, the correct data file locations
are set, and other settings are available. The
relationship between Windows, the
Registry, and applications is shown in Figure 1.2.
Figure 1.2. Windows
uses the Registry to control applications.
The Registry holds information about default data and auxiliary file locations, menus,
button bars, window status, and other options. It also holds installation information
such as the date
of installation, the user who installed the
software, the version number and date,
and sometimes the serial number. Depending on the actual software installed, it may
contain other application-specific information.
Although, in general, the Registry controls all 32-bit applications and drivers, the type of control it exercises is based on users and computers, not on applications or drivers. Every Registry entry controls a user function or a computer function. User functions would include the desktop appearance and home directory, for example. Computer functions are related to installed hardware and software, items that are common to all users.
Some application functions affect users, and others affect the computer and are not specifically set for an individual. Similarly, drivers may be user-specific, but, most of the time, they are for general use by the computer. All of the settings discussed in the rest of the book are separated by user and computer.
Some examples of user-type functions controlled by the Registry are
Some of those functions are the same regardless of user; others are user-specific.
Computer-related control items are based on the computer name, without respect to the logged-in user. An example of this type of control would be installing an application. The availability and access to the application is constant, regardless of the user; however, icons to launch the application are dependent on the user logging in to the network. Network protocol availability and priority is based on the computer, but current connections are based on user information.
Here are some examples of computer-based control items in the Registry:
Because every system has a set of Registry files for itself, any user who uses that machine will be bound by those settings. The settings are unique to that system. This is one of the reasons that every system should have its Registry protected through secure backups (see Chapter 4, "Protecting the NT Registry," and Chapter 6, "Protecting the Windows 95 Registry").
By default, Windows 95 user information is stored at each individual machine.
Because
Windows NT was designed as a network-connected (rather than a stand-alone) system,
the
Registry information for NT users can be stored in the domain controller (the
primary information in the primary domain controller, and a copy of it in each of
the backup domain controllers). Placing the user information in the domain controller
for
centralized use is called roaming profiles. If roaming profiles are used, as
a user logs in to the network, the Registry settings for that user are transferred
or mapped to the system where the user has logged in and are used there.
If the NT system is not part of a domain, but is used as a stand-alone system or part of a workgroup, the user's information is stored at the local machine (just as it is with 95), will not be transferred to another system, and is not available to any other system on the network. Each machine is fully independent of the others. If you created a "perfect" desktop setting on one system in the workgroup's network, it would not be available to any other system. On a domain, on the other hand, it is possible to transfer those settings from system to system.
Without the Registry, Windows 95 and Windows NT would not be possible. They are too complex to be controlled by the older .INI files, and their expansion capabilities allow almost unlimited installation and use of applications. The Registry is, however, much more complex than the .INI files, and understanding how it works, what it does, and how to work with it is critical for effective system administration.
The Registry controls all 32-bit applications and their functions on the system, plus the interaction between multiple applications, such as copying and pasting. It also controls all the hardware and drivers. Though most of the settings are made during installation and through the Control Panel, understanding the Registry is fundamental to reliable and capable management of Windows NT and Windows 95 systems.
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