So I am trying to make a recursion function, to convert a positive decimal to binary but I seem to be having problems. For the output the binary isn't displayed. "Binary is: " is just empty or blank. If anyone can help and explain why my binary is not displaying I would appreciate it!
I think your binary() function should directly output the digit. Put the cout inside the function. You may need to re-arrange the logic slightly in order to get the digits output in the correct order. Make the return type void as the function won't return a particular value - though a return statement will probably still be useful or necessary for correct logic.
Or alternatively (a bit more complicated, in my opinion) have the function return a string, which would be built by concatenating '1' or '0' characters as appropriate.