Put all the other files with an .lst extension in your INT List folder too, since they contain valuable information. Make sure to read the file Interrup.pri which is Ralf's Interrupt Primer.
4) Extract the files from rbilv21.zip into your INT List folder and run the Win 32 program RBILVIEW.exe which is a Windows viewer for Ralf's INTERRUP.LST file, Ports.lst and all the other .lst files. Open Ralf's Interrup.lst file with the viewer, it will build an index file to use for searches. Next time you want to write some ASM code, try searching through Ralf's INT List for all the details of what must be included for a particular INT function.
There's one more 'RBIL viewer' (called ILINA) that I think you'll find useful for doing lots of quick look-ups (it's easy on the eyes too). Extract Ilina100.zip from Part E (inter61e.zip), then finally extract all of its files into your INT List folder. Simply run the program (there's one little thing that bugs me about Ilina though: It's difficult to read the last line of any entry that goes beyond the window's bottom border; and there aren't any scroll bars for this either. You must grab the text itself with the mouse and/or use Arrow/PageUP/DN keys to get to the hidden lines.)