Ah, okay, so when you save the file in your editor, you’ll need to make sure that you can navigate to that same directory, or folder, where that file is.
You don’t need Ruby to write Crystal, it’s just very familiar to those who have. Both are relatively simple. Everything can seem overwhelming and alien when you are first getting started, just try and push through it and be okay with not knowing certain things.
So, if you are on macOS/Linux, you can type ls at the command prompt to list out the contents of that directory, and you can use cd to navigate inside a directory. So, if I wanted to go from Home/ → Home/code/ I’d type cd code from the Home directory. You can also type cd .. to go “up” one level. So, from Home/code/ if I typed cd .. I’d be back in Home/
These are pretty basic concepts for navigating. Try and navigate into the directory where your crystal_tut.cr file is from wherever your command prompt is opened. Your editor should say somewhere the filepath where the file is being saved. (sorry, never used Atom)