calculator AI2 source code

I thank you all for this great project.
(MIT App Inventor 2)
I'm a newby and I'd like to find some
source code to practice with a calculator

I found some sourcecode here
http://gallery.appinventor.mit.edu/#page%3DApp%26uid%3D127005%26label%3DMy%20Calculator%20with%20TTS

I changed the extention .zip into .aia and imported in project,
but I can't the block (code), I see only the design.

Where do I can find an example of code for AI2?

Another thing I'd like to do, is to add to the calcualator
to test storage:
log all the input and output ...

Thank you in advance for any help,

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sorry for posting,
I found an example here: AI2: MyCalculator: A simple four-function calculator

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