How does the compare function in qsort work?

Question

I found this sample code online, which explains how the qsort function works. I could not understand what the compare function returns.

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Answer 1

a and b are being compared as integers - they have to be passed in as void * but are then cast to int * before finally being deferenced. As for the return value, it will either be positive, negative, or zero, all of which would be taken into account in the sorting function.