How to solve 'Unrecognized Function or Variable' Error Code

I have code directly copied from my professor that pulls from five other functions to solve an IVP using Euler method. When I try to run the final code I get the 'Unrecognized function or variable' error. Is this because the final code does not have an actual defined function?

Answer 1

[Steven Lord]

Are you trying to run the script from inside the ZIP-file, without extracting it? That won't work. Extract the files to a directory, make the files in that directory accessible to MATLAB (making it your current directory or adding it to the MATLAB path), and then you should be able to run the script.

[Sarah Trentacoste]

How would I extract the files? I should also say that when I ran the DecayProblem_Euler file it worked and I downloaded all of the files from a ZIP-file, it is just the DecayProblem_Euler_Err file that won't run.