12 September, Day 5
Handout – mathematic induction
Written Assignment #1 due (on Chemnitz/Student Data)
Return/Review Systems Assignment #0 (great ideas – Post)
“professional programming practice”
Written Assignment #2 (chapter 10) assigned – due in one week, Day 7
System Assignment #1 (first presentation) topic due next time
Chapter 10
Program Correctness
Two Approaches
1. Testing
recall issues of testing from CSC370
{Test Data Set} (input) -> [Program] -> Verify Output
Outputs are compared to expected (ie True results)
hard: must determine expected outputs beforehand
(manually)
hard: what’s a “good” test data set to use?
Problem:
much manual effort required – must know expected results
a. most real world programs are too large to fully test
ex: an air traffic control system
how many possible configurations of planes?!
b. testing can only show that errors exist – it can not show that
there
are NO errors
purpose of testing is to find and identify errors
a good test finds an error
testing can not show that a program is correct
2. Proof
work of CAR Hoare (1960s)
“proofs” are inductive after assertions are made on program
structure
model: - make assertions
- prove (inductively) program structure is correct
Important as some programs are critical (ex: medical diagnostic,
flight
avionics, etc) – impossible to test completely
proof is a rigorous, mathematical analysis of the algorithm (code)
Read, beginning on page 63
CSC 490 Course Notes and Outline, © Dr. Gary Locklair, Fall 2006
