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     Topic links:
     
     what is the registry?
     
     what form does it take?
     
     the physical structure
     
     what's in the root keys?
     
     registry aliases
     
     
     
     
     
     
     Leaf through almost any edition of PC User (or most other computer
     magazines or Windows help sites) and you're bound to come across a
     bunch of techniques and tips which involve editing the Registry.
     Each of those tips carries a rider about the inherent dangers of
     the process.
     
     If you've been intimidated by the warnings and shied away, or if
     you've ignored the perils and tinkered with the Registry without
     really knowing much about it, now is a good time to become more
     familiar with this core component of Windows.
     
     What is the Registry?
     
     The Registry is the central repository for configuration data –
     user settings and machine-dependent settings – in Windows. It
     keeps track of installed programs; program interactions; hardware
     configuration; individual user preferences; and system
     customisations. Most of the information in the Registry is placed
     there automatically by Windows itself, and by utilities and
     applications via their setup routines and optional settings. It's
     also possible to edit Registry data directly.
     
     The Registry, introduced with Windows 95, replaced the old INI
     files used to store configuration settings. INIs were handy
     because they were short text files, easily edited with Notepad.
     But they had many limitations including size restrictions, lack of
     internal organisation and lack of support for multiple users and
     alternative hardware configurations. The Registry does away with
     all these limitations and makes it easier to track changes and
     recover settings after a crash.
     
     What form does it take?
     
     The Registry is organised as a hierarchical database. That simply
     means the information is stored in a tree-like structure, somewhat
     similar to the hierarchy you're familiar with through using
     Windows Explorer:
     
     FOLDER -> SUB-FOLDER -> FILE
     
     In the Registry, the hierarchy goes:
     
     KEY -> SUBKEY -> VALUE
     
     with each key having one or more subkeys and each subkey
     containing a value.
     
     Each value is stored with a value name and value data. The data
     also has a data type which identifies the kind of information –
     string, binary and so on – stored in the value.
     
     There are six main keys, also known as the root keys. They are:
     

     HKEY_CLASSES_ROOT

     HKEY_CURRENT_USER

     HKEY_LOCAL_MACHINE

     HKEY_USERS

     HKEY_CURRENT_CONFIG

     HKEY_DYN_DATA


     We'll look at each of these root keys shortly.
     
          
     
     The Registry displayed in the Registry Editor, with all root keys
     except HKEY_CLASSES_ROOT expanded to show the major subkeys. Click
     the image to see a full-size screenshot.
     
     The physical structure
     
     So much for the logical organisation of the Registry. Physically,
     the Registry is stored on your hard drive in two or more files:
     
     System.dat contains the hardware- and computer-specific Registry
     data
     User.dat contains user-specific information.
     In Windows Me, there's a third file called Classes.dat, which
     stores the HKEY_CLASSES_ROOT data. In network environments,
     there's often another registry file, Policy.pol, which contains
     network or company-wide settings established by the system
     administrator.
     
     What's in the root keys?
     
     Everything in the Registry branches out from the six root keys,
     whose names all begin with HKEY (it stands for handle to a key,
     which is programmer's terminology).
     
     HKEY_CLASSES_ROOT contains information pertaining to OLE (object
     linking and embedding), file association mappings, Windows
     shortcuts and some other aspects of the user interface.
     
     In HKEY_CLASSES_ROOT you'll find the names of all registered file
     types (such as .doc, .exe, .html and so on) and their associated
     properties. This key is, in fact, a pointer to another subkey,
     HKEY_LOCAL_MACHINE\Software\Classes.
     
     HKEY_CURRENT_USER contains user-specific information. The contents
     of this key are derived from information in the HKEY_USERS key at
     logon time.
     
     HKEY_LOCAL_MACHINE contains computer-specific information,
     including info about installed hardware and software settings. The
     information in this key is used by all users of the computer.
     
     HKEY_USERS contains user information such as default application
     settings, desktop configuration and so on. Some of the information
     is user-specific and some is available to all users of the
     computer. The default, generic settings are stored in a subkey
     HKEY_USERS\.DEFAULT. A new subkey is created for each user who
     logs onto the computer. At first, that new subkey contains a copy
     of the contents of the .DEFAULT subkey. As the user changes
     desktop and application settings, those changes are stored in the
     user's subkey.
     
     HKEY_CURRENT_CONFIG handles Plug & Play settings and information
     about multiple hardware configurations. Settings in this key are
     derived from a subkey of HKEY_LOCAL_MACHINE\Config.
     
     HKEY_DYN_DATA maintains a dynamic record of the current status of
     the computer.
     
     Registry aliases
     
     Although we talk about the six root keys in the Registry, there
     are really only two keys – HKEY_LOCAL_MACHINE and HKEY_USERS.
     Three of the four 'non-real' keys are aliases, the Registry
     equivalent of Windows shortcuts, deriving their contents from
     subkeys of LOCAL_MACHINE and USERS. Anything you change in one key
     is reflected in its alias. The fourth 'non-real' key,
     HKEY_DYN_DATA, is created on-the-fly from device status
     information each time the computer boots.
     
     Alias

Branch from which alias is derived
     HKEY_CLASSES_ROOT

HKEY_LOCAL_MACHINE\Software\Classes
     HKEY_CURRENT_USER

HKEY_USERS\username
     HKEY_CURRENT_CONFIG

HKEY_LOCAL_MACHINE\Config\profile

     Coming up
     
     In the second part of this series (which I'll publish in the next
     few weeks) we'll delve more deeply into the Registry courtesy of
     Regedit, the Registry Editor.

c 2002  Rose Vines

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※ 來源: DISP BBS (http://disp.twbbs.org)
※ 作者: ott  來自: 118.166.9.59  時間: 2010-01-16 23:53:30