You really should take the LabVIEW tutorials then.
LabVIEW Introduction Course - Three Hours
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And if you search for "uninitialized shift register", you should be able to find 100's of threads that will provide you information.
You do it by wiring a constant to the shift register on the left hand side outside of the loop.
But I don't know what your VI's do, so they might need the uninitialized shift register for the VI to work properly.
In which case you can use the First Call? primitive inside of the loop to determine whether you want to use the data from the shift register, or from your constant.
