Cse120wi11lec22[1] Debugging

8/6/2019 Cse120wi11lec22[1] Debugging

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Debugging warm-up activity find a partner find the bugs (errors) in the Scratchcode it is okay if you dont come up with the

Scratch solution but you should talk

with you partner about the bug and howeach of you might fix it

hint: there is no one right answer!Friday,February24,2011 SlidesbySusanEvans 1


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Possible Scratch Solutions

Friday,February24,2011 SlidesbySusanEvans 2


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What process did you follow

when looking for bugs?



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?

term coined by Grace Hopper in the1940s when she found a moth in theMark II computer she was working on

the moth was jammed in one of therelays causing the computer to fail

debugging: method of figuring out why aprocess or system doesnt work properly.



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Debugging

will be talking about 2 overall themesthroughout the lecture

debugging software/hardware you usein everyday life but do not write or build

debugging code that you write (e.g.,Processing code)



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Who is to blame for bugs in

software? You! .. usually computers are predictable they do exactly what they are told to do computers cant think for themselves if they werent programmed to do it; they

will fail software errors are much more rare than

human errors!



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Consider 0s (zeros) and Os (ohs)

or even ls (els) and 1s (ones) for thatmatter

what if the user types in an oh whenthey mean a zero

how could the computer be programmedto figure it out?



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Consider 0s (zeros) and Os

(ohs) could be programmed to converted ohs to

zeros

but what if each has a different meaning can you think of any situations where it

would be important to know which one theuser entered?

now it becomes very important for the userto be very precise when enteringinformation



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Debugging in Everyday Life

you more than likely have debugged longbefore the start of learning Processing inthis class

can you think of anything you havedebugged?



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Debugging Process

1. run the program; reproduce the sameexact error

2. state/determine the error 3. eliminate the obvious cases 4. Divide! Eliminate the parts of code that

work properly

5. Go back to step 1



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Debugging Process

1. run the program; reproduce the sameexact error

why?



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Debugging Process

2. state/determine the error 3. eliminate the obvious cases how do we do this in Processing? in

Scratch?



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Debugging Process

4. Divide! Eliminate the parts of codethat work properly

why would this make it easier? lets take a look at Chelsey and Lisas

code

they have a bug, but there code is 7pages long! we need to narrow down theproblem.



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Debugging Process

in groups of 3 or 4 find the bug in theircode

fix it on paper Chelsey & Lisa prepare a brief

explanation to give to the class about

the bug once they have found it



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Debugging Process

5. Go back to step 1 why? When should you stop the process?



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User Friendly Programing

how can you write user friendly code sothat the user knows when they haveentered bad information?

lets take a look at Shari and Stefanscode


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Cse120wi11lec22[1] Debugging