The applet on this page is a processor for the "straight-line programming language" (print and assignment statements) described in the Modern Compiler Implementation in Java book (chapter 1). Enter in any valid program in the language, and this applet gives the corresponding abstract syntax tree (in roughly the same form as the one at the top of page 12).

Just type the program in the top box, hit the "Parse Program" button and the abstract syntax should appear in the bottom box. I've put in the example from the book - try changing this to see what happens...