Spellcheck Program in C

/*So obviously the FILEPATH macro here would need to be changed for implementation, but here is a program I wrote this week that works with a dictionary to test if a user's input is in the given dictionary or not
*/

//Help Users Spell Correctly

//Hailey Hanson
//February 9th, 2015
//Systems Programming CS 360

#include<stdio.h>
#include<ctype.h>
#include<string.h>
#include<stdlib.h>
#include<fcntl.h>
#include<errno.h>
#include <unistd.h>
#define RECORD_SIZE 16
#define FILEPATH "/home/hailey/Documents/Code/WSU-V/SystemsProg/SystemsProg/lib/webster"


char*word;
int fd;
char*buffer;

char* plainWord(char*original);
int ok(int fd, char*word);

int main(int argc, char**argv){

    if(argc!=2){
        fprintf(stderr, "single word argument required\n");
        exit(1);
        }

    word = argv[1];

    fd = open(FILEPATH, O_RDONLY, 0);
    if (fd<0){
        fprintf(stderr, "couldn't open file %s : %s\n", FILEPATH, strerror(errno));
        exit(2);
    }
  
    if (ok(fd, word)) printf("yes, %s was found\n",word );
    else printf("no, %s was not found\n",word);

    close(fd);


char* plainWord(char*original){

    int i=0;
    char*dest;
    dest = calloc(strlen(original), sizeof(char));

    while(i<RECORD_SIZE){

        if(isalpha(original[i])){
            dest[i] = original[i];
        }
        i++;
    }
    dest[RECORD_SIZE] = '\0'; //this has to do with the specific dictionary I was using

    return strdup(dest);//must compile with gnu99 for strdup to work correctly
}


int ok (int fd, char*word){

    char* want = word;//from user
    char*have; //from webster

    int bot = 0;
    int fileSize = lseek(fd, 0, SEEK_END);
    int top = fileSize/RECORD_SIZE;
    buffer = calloc(RECORD_SIZE, sizeof(char));
  
    while(bot<top){
        int mid = (bot+top)/2;
        lseek(fd, mid*RECORD_SIZE, SEEK_SET);//moves me to middle of file
        read(fd, buffer, RECORD_SIZE);//fills buffer with one line

        want = plainWord(word);
        have = plainWord(buffer);
        int compare = strcmp(want, have);

        if(compare == 0){
            return 1;
        }
        else if (compare<0){
            top = mid;
        }
        else if (compare>0){
            bot = mid+1;
        }
    }
    return 0;
}