/* Array search for a target value in an array */ 
#include <stdio.h> 
#define NSIZE 20 
#define NOT_FOUND -1   

int search(const int arr[], int target, int n); 

int 
main()
{
    int array[NSIZE], size, value, position;
    int i, num;
    FILE *fp; 
 
    fp = fopen("data.txt", "r");
    size = 0;
    while(fscanf(fp, "%d", &num) == 1)
        array[size++] = num;

    printf("The data array is = "); 
    for (i=0; i<size; ++i)
         printf("%3d",array[i]); 
         
    printf("\nPlease enter a target value (-1 = done)> ");
    scanf("%d", &value);
    while(value != -1)
    {
        position = search(array, value, size);
        if(position == -1)
            printf("%d is not in the array.\n", value);
        else
            printf("%d is located at position %d in the array.\n", 
                    value, position);

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

    fclose(fp); 
    return 0;
}

/* Searches for target item in first n elements of array arr */
int
search(const int arr[], int target, int n)
{
    int i, found = 0,  where; 

    i = 0;
    while (!found && i < n) {
        if (arr[i] == target)
            found = 1;
        else
            ++i;
    }

    if (found)
       where = i;
    else
       where = NOT_FOUND;

    return (where);
}