cat is a command used to display the content of the files in linux.
In windows cat command will not work.
Better would be simply open the file in some editor and view.
thanks a lot for your reply and make it very interactive to learn during this workshop
For Windows users
1- Download the code files from this tutorial video page
2- save the file primes.txt at default path for ipthon3 files(where the graph charts were saved in previous tutorials by default)
3- use command "!type primes.txt".