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     The bsearch function performs a binary search of a sorted array of
     <num> elements, each of <width> bytes in size. The <base> value is
     a pointer to the base of the array to be searched, and <key> is
     the value being sought.
 
     The <compare> argument is a pointer to a user-supplied routine
     that compares the key with an array element and returns a value
     specifying their relationship. The bsearch function calls the
     <compare> routine one or more times during the search, passing
     pointers to the key and an array element on each call. The routine
     must compare the two, then return one of the following values:
 
     Value              Meaning
 
     Less than 0        <key> less than <elem>
     0                  <key> identical to <elem>
     Greater than 0     <key> greater than <elem>
 
     If the array you are searching is not in ascending sort order,
     bsearch does not work properly. If the array contains duplicate
     records with identical keys, there is no way to predict which of
     the duplicate records will be located by bsearch.
 
     Return Value
 
     The bsearch function returns a pointer to the first occurrence of
     <key> in the array pointed to by <base>. If <key> is not found,
     the function returns NULL.
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