AdminXP.com: Environment Variables

Environment Variables

Variable- a term primarily known from programming. A variable is a memory space (storage) for a predefined type of data. A variable always has a name and represents some data or objects. In programming and in the Windows environment, there exist predefined variables that have been set by the creators to be used by the system or the user For example, using a string to the variable %SYSTEMROOT% you will get the path to Windows directory. Besides predefined variables, you can create your own, or they can be created and modified according to the requirements of a program or user. In case of a virus or incorrect variable values the system or program may not work correctly.
Environment Variables - predefined variables that are intended for saving system settings or string. Most variables are saved in Windows registry and most of them are set during the installation of the system or upon a user's or program's request. In the Windows system, you can either see user variables representing particular settings of each user or system variables intended for the system and all users. You can recognize the variable environment very easily - there is the "percentage" (%) character in front and behind the variable (%Variable%).

Variable management

Right click the icon Computer - Properties - Advanced - Environment Variables

Environment Variables

By marking a variable or using buttons you can add, modify or remove some variables

edit environment variables

Example of editing the "windir" variable after clicking the Edit button.

TIP: If we want to add a new variable MW in user variables with the value c:\MUJWEB, you can go to Start - Run and type %MW% to open a window with the content of the c:\MUJWEB directory.
Displaying and editing in the command line using the "set" command

C:\set
ALLUSERSPROFILE=C:\ProgramData
APPDATA=C:\Users\adminxp\AppData\Roaming
CommonProgramFiles=C:\Program Files\Common Files
COMPUTERNAME=ADMINXP-PC
ComSpec=C:\Windows\system32\cmd.exe
FP_NO_HOST_CHECK=NO
HOMEDRIVE=C:
HOMEPATH=\Users\adminxp
LOCALAPPDATA=C:\Users\adminxp\AppData\Local
LOGONSERVER=\\ADMINXP-PC
OS=Windows_NT
Path=C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
PROCESSOR_ARCHITECTURE=x86
PROCESSOR_IDENTIFIER=x86 Family 15 Model 79 Stepping 2, AuthenticAMD
PROCESSOR_LEVEL=15
PROCESSOR_REVISION=4f02
ProgramData=C:\ProgramData
ProgramFiles=C:\Program Files
PROMPT=$P$G
PUBLIC=C:\Users\Public
SystemDrive=C:
SystemRoot=C:\Windows
TEMP=C:\Users\adminxp\AppData\Local\Temp
TMP=C:\Users\adminxp\AppData\Local\Temp
USERDOMAIN=adminxp-PC
USERNAME=adminxp
USERPROFILE=C:\Users\adminxp
windir=C:\Windows

Example of displaying the settings of some system variables in the command line using the "set" command. For help, use the command "set /?".

To display particular variables, even those that are not visible after using the "set" command, you can use the "echo" command. E.g. echo %ALLUSERSPROFILE%

To modify, use the syntax SET [variable=[string]] - e.g. SET MW=C:\MUJWEB

Some values can be changed directly in the registry or through graphical environment and system tools or using other applications.
Changes can be made through login scripts or other scripts and batch commands (autoexec.bat in older systems).

List of primary variables of Windows Vista and Windows XP

%ALLUSERSPROFILE%	Path to the All User profile Vista - C:\ProgramData WindowsXP - C:\Documents and Settings\All Users
%APPDATA%	Path to the Application Data folder Vista - C:\Users\%USERNAME%\AppData\Roaming WindowsXP - C:\Documents and Settings\%USERNAME%\Application Data
%CD%	Path to the current directory.
%CMDCMDLINE%	Path to the launched operation in the Command Line / Cmd.exe program (C:\WINDOWS\system32\cmd.exe)
%CMDEXTVERSION%	Version number of the current Command Processor Extensions
%commonprogramfiles%	Path to the Common Files folder (Ex. C:\Program Files\Common Files)
%COMPUTERNAME%	Computer name
%COMSPEC%	Path to the command interpreter
%DATE%	Current date
%ERRORLEVEL%	Error code for the last used command (0 means OK)
%HOMEDRIVE%	Current home drive letter (according to the home directory)
%HOMEPATH%	Full path to the user's home folder.
%HOMESHARE%	Full network path to the user's home folder.
%LOCALAPPDATA%	(ex. C:\Users\%USERNAME%\AppData\Local)
%LOGONSERVER%	Name of the domain controller that validated the domain logon. If the domain is not available, name of the computer is displayed.
%NUMBER_OF_PROCESSORS%	Number of processors in the computer
%OS%	Name of the OS family (ex. Windows_NT - the same for XP and Vista)
%PATH%	Path to executable files. (if you define an executable program, it is launched without the need of specifying the full path).
%PATHEXT%	File types that are set as executable in the operating system.
%PROCESSOR_ARCHITECTURE%	Processor's architecture. (x86, IA64)
%PROCESSOR_IDENTFIER%	Processor's description.
%PROCESSOR_LEVEL%	Processor's model number
%PROCESSOR_REVISION%	Version number of the processor's hardware
%ProgramData%	New in Vista (ex. C:\ProgramData). The same as %ALLUSERSPROFILE%.
%PROGRAMFILES%	Path to the Program Files directory. (ex. C:\Program Files)
%PROMPT%	Setup of the current command intepreter (e.g. $P$G, more with "prompt /?")
%PUBLIC%	Represents the public folder for shared data (data which must be visible for all users within a computer or network). Newly in Vista (C:\Users\Public).
%RANDOM%	Generates a random decimal number within the range from 0 to 32767.
%SYSTEMDRIVE%	Denotes the drive that contains the root directory of the Windows system (ex. c:)
%SYSTEMROOT%	Location of the root directory of the operating system.
%TEMP% a %TMP%	Folder for temporary data. Some applications invoke the folder with the variable %TMP%, others use %TEMP%. (ex. C:\Users\%USERNAME%\AppData\Local\Temp)
%TIME%	Current time
%USERDOMAIN%	Name of the domain that contains the account of the currently logged in user. If the user is not a member of the domain, name of the computer will be displayed.
%USERNAME%	Name of the currently logged in user
%USERPROFILE%	Location of the current user's profile
%WINDIR%	Location of the operating system directory. %SYSTEMROOT% is a newer variable. %WINDIR% is used by older systems and applications.

Saving data and variables for all users - registry for Windows XP

Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders

Common AppData	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Application Data
Common Desktop	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Desktop
Common Documents	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Documents
Common Favorites	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Favorites
Common Programs	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Start Menu\Programs
Common Start Menu	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Start menu
Common Startup	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Start Menu\Programs\Startup
Common templates	REG_EXPAND_SZ	%ALLUSERSPROFILE%\Templates

Saving data and variables for all users - registry for Windows Vista

Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\explorer\User Shell Folders

Common AppData	REG_EXPAND_SZ	%ProgramData%
Common Desktop	REG_EXPAND_SZ	%PUBLIC%\Desktop
Common Documents	REG_EXPAND_SZ	%PUBLIC%\Documents
CommonMusic	REG_EXPAND_SZ	%PUBLIC%\Music
CommonPictures	REG_EXPAND_SZ	%PUBLIC%\Pictures
Common Programs	REG_EXPAND_SZ	%ProgramData%\Microsoft\Windows\Start Menu\Programs
Common Start Menu	REG_EXPAND_SZ	%ProgramData%\Microsoft\Windows\Start Menu
Common Startup	REG_EXPAND_SZ	%ProgramData%\Microsoft\Windows\Start Menu\Programs\Startup
Common templates	REG_EXPAND_SZ	%ProgramData%\Microsoft\Windows\Templates
CommonVideo	REG_EXPAND_SZ	%PUBLIC%\Videos
{3D644C9B-1FB8-4f30-9B45-F670235F79C0}	REG_EXPAND_SZ	%PUBLIC%\Downloads

Saving data and variables for all users - registry for Windows XP

Key: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurentVersion\Explorer\User Shell Folders

AppData	REG_EXPAND_SZ	%USERPROFILE%\Application Data
Cache	REG_EXPAND_SZ	%USERPROFILE%\Local Settings\Temporary Internet Files
Cookies	REG_EXPAND_SZ	%USERPROFILE%\Cookies
Desktop	REG_EXPAND_SZ	%USERPROFILE%\Desktop
Favorites	REG_EXPAND_SZ	%USERPROFILE%\Favorites
History	REG_EXPAND_SZ	%USERPROFILE%\Local Settings\History
LocalAppData	REG_EXPAND_SZ	%USERPROFILE%\Local Settings\Application Data
Local Settings	REG_EXPAND_SZ	%USERPROFILE%\Local Settings
My Pictures	REG_EXPAND_SZ	%USERPROFILE%\My Documents\My Pictures
NetHood	REG_EXPAND_SZ	%USERPROFILE%\NetHood
Personal	REG_EXPAND_SZ	%USERPROFILE%\My Documents
PrintHood	REG_EXPAND_SZ	%USERPROFILE%\PrintHood
Programs	REG_EXPAND_SZ	%USERPROFILE%\Start Menu\Programs
Recent	REG_EXPAND_SZ	%USERPROFILE%\Recent
SendTo	REG_EXPAND_SZ	%USERPROFILE%\SendTo
Start Menu	REG_EXPAND_SZ	%USERPROFILE%\Start Menu
Startup	REG_EXPAND_SZ	%USERPROFILE%\Start Menu\Programs\Startup
Templates	REG_EXPAND_SZ	%USERPROFILE%\Templates

Saving data and variables for all users - registry Windows Vista

Key: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders

AppData	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming
Cache	REG_EXPAND_SZ	%USERPROFILE%\AppData\Local\Microsoft\Windows\Temporary Internet Files
Cookies	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Cookies
Desktop	REG_EXPAND_SZ	%USERPROFILE%\Desktop
Favorites	REG_EXPAND_SZ	%USERPROFILE%\Favorites
History	REG_EXPAND_SZ	%USERPROFILE%\AppData\Local\Microsoft\Windows\History
LocalAppData	REG_EXPAND_SZ	%USERPROFILE%\AppData\Local
My Music	REG_EXPAND_SZ	%USERPROFILE%\Music
My Pictures	REG_EXPAND_SZ	%USERPROFILE%\Pictures
My Video	REG_EXPAND_SZ	%USERPROFILE%\Videos
NetHood	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Network
Personal	REG_EXPAND_SZ	%USERPROFILE%\Documents
PrintHood	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Printer
Programs	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Start
Recent	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Recent
SendTo	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\SendTo
Startup	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Start
Start Menu	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Start
Templates	REG_EXPAND_SZ	%USERPROFILE%\AppData\Roaming\Microsoft\Windows\Templates
{374DE290-123F-4565-9164-39C4925E467B}	REG_EXPAND_SZ	%USERPROFILE%\Downloads

Guide for beginners and administrators