Environment Variables in Windows XP

Environment variables have long been used in computer operating systems and are present in Unix, DOS, and Windows The word "environment" used in the context here refers to various features of the computer system and certain basic system data. Here is one of Microsoft’s definitions:

Environment variables are strings that contain information such as drive, path, or file name. They control the behavior of various programs. For example, the TEMP environment variable specifies the location in which programs place temporary files.

 

Variable
Typical value (May vary, depending on system)

%ALLUSERSPROFILE%
C:\Documents and Settings\All Users

%APPDATA%
C:\Documents and Settings\{username}\Application Data

%COMPUTERNAME%
{computername}

%COMSPEC%
C:\Windows\System32\cmd.exe

%HOMEDRIVE%
C:

%HOMEPATH%
\Documents and Settings\{username}

%PATH%
C:\Windows\System32\;C:\Windows\;C:\Windows\System32\Wbem

%PATHEXT%
.COM; .EXE; .BAT; .CMD; .VBS; .VBE; .JS ; .WSF; .WSH

%PROGRAMFILES%
Directory containing program files, usually C:\Program Files

%PROMPT%
Code for current command prompt format. Code is usually $P$G

%SYSTEMDRIVE%
The drive containing the Windows XP root directory, usually C:

%SYSTEMROOT%
The Windows XP root directory, usually C:\Windows

%TEMP% and %TMP%
C:\DOCUME~1\{username}\LOCALS~1\Temp

%USERNAME%
{username}

%USERPROFILE%
C:\Documents and Settings\{username}

%WINDIR%
C:\Windows

 

Some dynamic environment variables

%DATE%
Current date in the format determined by the Date command

%TIME%
Current time in the format determined by the Time command

%CD%
Current directory with its full path

%ERRORLEVEL%
Number defining exit status of a previous command or program

%RANDOM%
Random number between 0 and 32767

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