The default interface for editing MuPAD® code is the MATLAB® Editor. Alternatively, you can create and edit your code in any text editor. The MATLAB Editor automatically formats the code and, therefore, helps you avoid errors, or at least reduce their number.
To open an existing MuPAD file with the extension .mu in the MATLAB Editor, double-click the file name or select Open and navigate to the file.
After editing the code, save the file. Note that the extension .mu allows the Editor to recognize and open MuPAD program files. Thus, if you intend to open the files in the MATLAB Editor, save them with the extension .mu. Otherwise, you can specify other extensions suitable for text files, for example, .txt or .tst.