Let’s Build a Simple Interpreter, Part 18: Executing Procedure Calls

One way to get your feet wet is to write an eval function for a small language like "basic arithmetic language" in your programming language of choice. Allow only an int type, a few operators ( add, sub, mul ), etc. Then have eval parse then run a statement(s) from "basic arithmetic" and you'll get an idea of how interpreters work. From there you can delve into theory and writing interpreters for more complex languages. I believe in doing first and then learning theory after. Also, you can try writing eval in an OO language, functional language and procedural language to get a deeper grasp of the differences between these programming paradigms.