//binary search
#include <stdio.h>

int main()
{
   int i, first, last, middle, n, search, array[100];

   printf("Enter number of elements\n");
   scanf("%d",&n);

   printf("Enter %d elements\n", n);

   for ( i= 0 ; i< n ; i++ )
      scanf("%d",&array[i]);

   printf("Enter value to search\n");
   scanf("%d",&search);

   first = 0;
   last = n - 1;
   middle = (first+last)/2;

   while( first <= last )
   {
      if ( array[middle] < search )
         first = middle + 1;  
      else if ( array[middle] == search )
      {
         printf("%d found at location %d.\n", search, middle+1);
         break;
      }
      else
         last = middle - 1;

      middle = (first + last)/2;
   }
   if ( first > last )
      printf("Not found! %d is not present in the list.\n", search);

   return 0;  
}




Ouput
Enter number of elements
8
Enter 8 integers
74
41
12
23
36
69
98
85
Enter value to find
69
69 found at location 6.