There are two types of environment variables: user environment variables which are for the current user and system environment variables which are available to all users.

The user environment variables are stored in the following registry key:

HKEY_CURRENT_USER\Environment

The System environment variables are stored in the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment

Open a command prompt, type set, and press Enter to display all current environment variables on your PC.

You can open PowerShell and type Get-ChildItem Env:, and press Enter to display all current environment variables on your PC.

You may have more than this

Environment Variables Value
%ALLUSERSPROFILE% C:\ProgramData
%APPDATA% C:\Users\(user)\AppData\Roaming
%CD% (command prompt only) Current directory full path
%CMDCMDLINE% (command prompt only) Returns exact command line used to start current cmd.exe session.
%CMDEXTVERSION% (command prompt only) Number of current command processor extensions.
%CommonProgramFiles% C:\Program Files\Common Files
%CommonProgramFiles(x86)% C:\Program Files (x86)\Common Files
%CommonProgramW6432% C:\Program Files\Common Files
%COMPUTERNAME% The computer name of the current local system.
%COMSPEC% C:\Windows\System32\cmd.exe
%DATE% (command prompt only) Current date in format determined by Date command
%DriverData% C:\Windows\System32\Drivers\DriverData
%ERRORLEVEL% (command prompt only) Number defining exit status of previous command or program
%HOMEDRIVE% C:
%HOMEPATH% \Users\(user)
%LOCALAPPDATA% (user)\AppData\Local
%LOGONSERVER% \\MicrosoftAccount
%NUMBER_OF_PROCESSORS% 12
%OneDrive% Current OneDrive folder location like C:\Users\user\OneDrive
%OS% Windows_NT
%PATH% C:\WINDOWS
C:\WINDOWS\system32
C:\WINDOWS\System32\Wbem
C:\WINDOWS\System32\WindowsPowerShell\v1.0
%PATHEXT% COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
%PROCESSOR_ARCHITECTURE% AMD64
%PROCESSOR_IDENTIFIER% AMD64 Family 23 Model 113 Stepping 0, AuthenticAMD
%PROCESSOR_LEVEL% 23
%PROCESSOR_REVISION% 7100
%ProgramData% C:\ProgramData
%ProgramFiles% C:\Program Files
%ProgramFiles(x86)% C:\Program Files (x86)
%ProgramW6432% C:\Program Files
%PROMPT% (command prompt only) Code for current command prompt format. Code is usually $P$G
%PSModulePath% C:\Windows\system32\WindowsPowerShell\v1.0\Modules\
%PUBLIC% C:\Users\Public
%RANDOM% (command prompt only) To get random number between 0 and 32767
%SessionName% When logging on directly to machine, returns “Console”.

When client connects via terminal server session, is combination of
connection name, followed by pound symbol {#} and session number.

%SystemDrive% C:
%SystemRoot% C:\Windows
%TEMP% C:\Users\(user)\AppData\Local\Temp
%TIME% (command prompt only) Current time in format determined by Time command
%TMP% C:\Users\(user)\AppData\Local\Temp
%USERDOMAIN% The network domain name associated with the current user.
%USERDOMAIN_ROAMINGPROFILE% The network domain name associated with the current roaming profile.
%USERNAME% (user)
%USERPROFILE% C:\Users\(user)
%WINDIR% C:\Windows