%cd% 于%~dp0的差别

%cd% is available either to a batch file or at the command prompt and expands to the drive letter and path of the current directory (which can change e.g. by using the CD command)
%~dp0 is only available within a batch file and expands to the drive letter and path in which that batch file is located (which cannot change). It is obtained from %0 which is the batch file's name.
An experiment like the following shows the difference
Here is D:\dirshow.bat:

Code:

@echo off
echo this is %%cd%%  %cd%
echo this is %%~dp0 %~dp0

Run it from C:\ and this is what you see

Code:

C:\>D:\dirshow.bat
this is %cd%  C:\
this is %~dp0 D:\