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Back to Some Reliability Considerations. On to The Costs of Reliability.

**Held** Tuesday, March 14, 2000

**Overview**

Today, we consider one way that we might make programs more reliable: by proving them correct.

**Question 30 for today's class**:
*What do we mean when we say a program is "correct"?*

**Question 31 for Wednesday's class**: *How do we balance the need for formal specifications required by program proof techniques and the complexity of modern graphical applications?*

**Notes**

- On Friday, we'll work on BillMan. You may want to start thinking about what features you'd like to see in BillMan.

**Contents**

**Summary**

- What does it mean that a program is correct?
- How do we prove that a program is correct?
- Example (from the book): GCD

- Can we show that a nontrivial program is correct?

- We begin with the question I asked you for today: What does
it mean when we say that a program is
*correct*? - There are many different perspectives on this issue. We'll look at some.

- To many mathematically-oriented folks, a program is correct
when we can prove that it does the correct thing
- Most typically, that the output is correct for every reasonable input

- I'm assuming that most of you did not successfuly follow the proof in the textbook, so we'll try it.
- We may also do a more formal proof for binary search.

- Can we apply this technique to all programs? Why or why not?

Saturday, 22 January 2000

- Created as a blank outline.

Tuesday, 14 February 2000

- Filled in the details.

Back to Some Reliability Considerations. On to The Costs of Reliability.

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**Disclaimer** Often, these pages were created "on the fly" with little, if any, proofreading. Any or all of the information on the pages may be incorrect. Please contact me if you notice errors.

This page may be found at http://www.math.grin.edu/~rebelsky/Courses/CS105/2000S/Outlines/outline.30.html

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