Thread: Program throwing warning implicit declaration of function error

I am having trouble finding the cause of this error. It is a program that involves a binary search.

Code:

#include <math.h>
#include <stdio.h>


/* selection sort of an array */
#include <stdio.h>
#define NSIZE 1000
int get_min_range(int list[], int first, int last);
void select_sort(int list[], int n);

int
main()
{
   int array[NSIZE], size, num, i;
   FILE *fp;

 fopen("data.txt", "r");
   size = 0;
   while(fscanf(fp, "%d", &num) == 1)
       array[size++] = num;

   printf("\narray before sorting  = ");
   for (i = 0; i < size; ++i)
       printf("  %d",array[i]);

   select_sort(array, size);  // selection sort

   printf("\narray after sorting = ");
   for (i = 0; i < size; ++i) {
       printf("  %d",array[i]); }

       int input;


       printf("\nPlease enter a value (-1 = done)> ");
       scanf("%d", &input);

       while (input != -1) {
       int x = search(array, input, size);
               printf("%d is located at  position in the array after %d comparisons \n", input, x);
               printf("Please enter a value (-1 = done)> ");
               scanf("%d", &input);

       }



   fclose(fp);
   return 0;
}
/* sort array list[] by selection sort */
void
select_sort(int list[], int n)
{
   int cur_index, temp, index_of_min;

   for (cur_index = 0; cur_index < n-1; ++cur_index) {
       /* Find position of smallest element in unsorted subarray */
       index_of_min = get_min_range(list, cur_index, n-1);
       /* Exchange elements at fill and index_of_min */
       if (cur_index != index_of_min) {
           temp = list[index_of_min];
           list[index_of_min] = list[cur_index];
           list[cur_index] = temp;
       }
   }
}
/* Find the position of the smallest element in the subarray */
int
get_min_range(int list[], int first, int last)
{
     int i, index_small, temp;

     temp = list[first];
     index_small = first;
     for  (i = first;  i <= last;  ++i)
         if (list[i] < temp){
               temp = list[i];
               index_small = i;
         }

     return (index_small);
}


int
search(const int arr[],  //input - array to search
int    target,           //input - value searched for
int    n)                //input - number of elements to search
{
    int i,
         found = 0,     //whether or not target has been found
         where;         //index where target found or NOT_FOUND

i = 0;
int max = n-1;
int min = 0;
int middle;
int count = 0;
while (!found && min < max) {
       count = count + 1;
       middle = min + (max-min)/2;
      if (arr[middle] == target)
          found = 1;
      else if (target > arr[middle])
               min = middle +1;
       else
               max = middle - 1;
         ++i;
}

if (found)
    where = count;
else
    where = -1;

return (where);

}

Help please, I cannot figure out where it goes wrong.

Code:

 #include <math.h>
#include <stdio.h>


/* selection sort of an array */
#include <stdio.h>
#define NSIZE 1000
int get_min_range(int list[], int first, int last);
void select_sort(int list[], int n);

int search(const int arr[],  //input - array to search
int    target, int n)   ;       //input - value searched for

int main()
{
   int array[NSIZE], size, num, i;
   FILE *fp;

 fopen("data.txt", "r");
   size = 0;
   while(fscanf(fp, "%d", &num) == 1)
       array[size++] = num;

   printf("\narray before sorting  = ");
   for (i = 0; i < size; ++i)
       printf("  %d",array[i]);

   select_sort(array, size);  // selection sort

   printf("\narray after sorting = ");
   for (i = 0; i < size; ++i) {
       printf("  %d",array[i]); }

       int input;


       printf("\nPlease enter a value (-1 = done)> ");
       scanf("%d", &input);

       while (input != -1) {
       int x = search(array, input, size);
               printf("%d is located at  position in the array after %d comparisons \n", input, x);
               printf("Please enter a value (-1 = done)> ");
               scanf("%d", &input);

       }



   fclose(fp);
   return 0;
}
/* sort array list[] by selection sort */
void
select_sort(int list[], int n)
{
   int cur_index, temp, index_of_min;

   for (cur_index = 0; cur_index < n-1; ++cur_index) {
       /* Find position of smallest element in unsorted subarray */
       index_of_min = get_min_range(list, cur_index, n-1);
       /* Exchange elements at fill and index_of_min */
       if (cur_index != index_of_min) {
           temp = list[index_of_min];
           list[index_of_min] = list[cur_index];
           list[cur_index] = temp;
       }
   }
}
/* Find the position of the smallest element in the subarray */
int
get_min_range(int list[], int first, int last)
{
     int i, index_small, temp;

     temp = list[first];
     index_small = first;
     for  (i = first;  i <= last;  ++i)
         if (list[i] < temp){
               temp = list[i];
               index_small = i;
         }

     return (index_small);
}


int
search(const int arr[],  //input - array to search
int    target,           //input - value searched for
int    n)                //input - number of elements to search
{
    int i,
         found = 0,     //whether or not target has been found
         where;         //index where target found or NOT_FOUND

i = 0;
int max = n-1;
int min = 0;
int middle;
int count = 0;
while (!found && min < max) {
       count = count + 1;
       middle = min + (max-min)/2;
      if (arr[middle] == target)
          found = 1;
      else if (target > arr[middle])
               min = middle +1;
       else
               max = middle - 1;
         ++i;
}

if (found)
    where = count;
else
    where = -1;

return (where);

}

now its saying warning fp is used uninitialized in this function on line 21. Does this mean that my file is missing from my directory?