403 lecture 2

Preliminaries:

Many people spoke in class last week.  Great!  But others did not.


Followups from last class:

I have a confession:
Last class, I lied.
It is actually possible for testing to return "yes" to the question "is my program correct?".



Our analysis of even vs. odd:

"even", "odd", "unknown" is an abstraction.

What is abstraction?
What is a model?
We talked about the purpose of building a model.
What are the differences between a model airplane and a real airplane?


We will "run" the program.
The semantics of the operation is called a "transfer function".
Examples:  +, *, /

 * the analysis had *one job*, (tell us if the answer is even or odd), and it didn't do it.

 * we got an exact answer by writing a full symbolic representation of the program's output
    * what is the problem with that?  What is a concrete example?


[To do: add text for the board, to make the lecture more specific
and convey the ideas more effectively.]


Now, go to lecture slides
[To do:  add a picture for Purify/LCLint analysis.]