[Tutor] Highlighting instructions: pedagogical preferences

[André Roberge]

I'm writing a program "interpreter" which has two windows: a program 
editing window and a program output window.

The interpreter can either step through the program automatically, at a 
slow pace, or step through the program one instruction at a time, as the 
user "clicks" on a "step button".

The instructions being executed are highlighted one by one.

Question: should the highlighted instruction be the one that has just 
been executed, or the one that is about to be executed (when the user 
clicks on the step button, for example)?

At present, I have implemented the second method.  I'm wondering if 
that's the best choice.

Any ideas?

André

P.S.  Btw, this program is part of a python tutorial I am writing - 
hence the relevance to this list :-)