stupid question

I am really, really new with database and am learning it. There are some things I am still confused about. Can someone please shed a light on me? Ok, here we go: 1. What is the difference between isql and r4gl? Do they interact with each other when run, or what?? 2. Why do they need a temporary directory? What is it for? 3. What actually happens to the database when a program runs? Will it be that only certain tables are loaded, or everything is loaded into memory? I have the book INFORMIX-4GL by Example, but I can't find any information about those questions (well, ok, it's not stupid question, but stupid questionS ...:) Thank you for any reply The Bewildered heidi