系统变量的表示方法

default values of environment variables under English versions of Windows link
在CMD中输入set得到(link)

Variable	Locale specific	Windows Vista/7/8 (CMD)
%COMPUTERNAME%	No	{computername}
%HOMEDRIVE%, %SystemDrive%	No	C:
%USERDOMAIN%	No	{userdomain}
%USERNAME%	No	{username}
%LOGONSERVER%	No	\\{domain_logon_server}
%ALLUSERSPROFILE%, %ProgramData%	Yes	C:\ProgramData
%PUBLIC%	Yes	%SystemDrive%\Users\Public
%HOMEPATH%	Yes	\Users\{username}
%USERPROFILE%	Yes	%SystemDrive%\Users\{username}
%APPDATA%	Yes	C:\Users\{username}\AppData\Roaming
%LOCALAPPDATA%	Yes	C:\Users\{username}\AppData\Local
%ProgramFiles(x86)%	Yes	%SystemDrive%\Program Files (x86) (only in 64-bit version)
%CommonProgramFiles(x86)%	Yes	C:\Program Files (x86)\Common Files (only in 64-bit version)
%ProgramFiles%, %ProgramW6432%	Yes	%SystemDrive%\Program Files
%CommonProgramFiles%	Yes	C:\Program Files\Common Files
%CommonProgramW6432%	Yes	C:\Program Files\Common Files (only in 64-bit version)
%PSModulePath%		%SystemRoot%\system32\WindowsPowerShell\v1.0\Modules
%ComSpec%	No	C:\Windows\System32\cmd.exe
%PATH%	Yes	C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;{plus program paths}
%PATHEXT%	No	.com;.exe;.bat;.cmd;.vbs;.vbe;.js;.jse;.wsf;.wsh;.msc
%PROMPT%	No	Code for current command prompt format, usually $P$G
%SystemRoot%, %windir%	No	%SystemDrive%\Windows
%TEMP% and %TMP%	Yes	%SystemRoot%\TEMP (for system environment variables %TMP% and %TEMP%), %USERPROFILE%\AppData\Local\Temp (for user environment variables %TMP% and %TEMP%)