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 qsort()                 Perform Quick Sort

 #include   <search.h>                   Required for declarations only
 #include   <stdlib.h>                   For ANSI compatibility

 void       qsort(base,num,width,(compare()));
 void       *base;                       Pointer to base of search data
 size_t     num, width;                  Number and width of elements
 int        (*compare)(e1,e2);           Pointer to compare function
 const void *e1, *e2;                    Array elements

    qsort() sorts an array of 'num' elements by means of a quick-sort
    algorithm.  Each element is 'width' bytes in size.  'base' points to
    the base of the array to be sorted.  The sorted elements overwrite
    the elements in the array.

    'compare' points to a routine supplied by the user.  qsort() calls
    the routine one or more times, each time passing it pointers to two
    array elements to be compared.  'compare' returns one of the
    following values, based on the results of the comparison:

                  < 0        'element1' <  'element2'

                    0         'element1' == 'element2'

                  > 0         'element1' >  'element2'

    Returns:    No return value.

   -------------------------------- Example ---------------------------------

    The following statements print out an array, sort the array and print
    it again.

           #include <search.h>
           #include <stdio.h>
           #include <string.h>

           int vals[] = {10,90,30,70,50,60,40,80,20,100};
           int num = 10, x;
           int cmp();

           main()
           {
               for (x = 0; x < num; x++)
                   printf("%d ",vals[x]);
               printf("\n");
               qsort(vals,num,sizeof(int),cmp);
               for (x = 0; x < num; x++)
                   printf("%d ",vals[x]);
           }

           int cmp(n1,n2)
           int *n1;
           int *n2;
           {
               return(*n1 - *n2);
           }