binary sorting and searching

#include <stdio.h>s

void main()
{
   int c, first, last, middle, n, search, arr[20];
   printf("Enter 20 integers\n");

   for (c = 0; c < 20; c++)
      scanf("%d",&arr[c]);

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

   first = 0;
   last = 19;
   middle = (first+last)/2;

   while (first <= last)
{
      if (arr[middle] < search)
         first = middle + 1;  
      else if (arr[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);

   getch();
}