The default search path changes for each MATLAB® version because the default folders that come with the products change. Different MATLAB versions cannot use the same pathdef.m file.
To use your files with a new MATLAB version or with multiple versions, do one of the following:
For each version, add the folders containing your files to the search path. Save the search path (that is, save the pathdef.m file) where that version of MATLAB can access it.
Include addpath statements in the startup.m file. Use the same startup.m file with the multiple versions of MATLAB.
Including addpath statements in the startup.m file also allows you to use your files with MATLAB on different platforms.