// Global variables and arrays for simple access
char buffer[LENGTH+1]; // Declares the buffer to store one line or one word in total
int wordcount = 0;
int hash_index;

node* head_array[HASHTABLE_SIZE] = {NULL}; // Stores pointer to node datatype
node* head_node;  // Will always be the most recent node, and first in the list
FILE* dict_file;


/**
 * Returns true if word is in dictionary else false.
 */
bool check(const char* word)
{
    for (int i = 0, wordlen = strlen(word); i < wordlen; i++) {
        buffer[i] = tolower(word[i]);
        buffer[i+1] = '\0';
    }

    hash_index = hash(buffer);
    head_node = head_array[hash_index];

    while (head_node != NULL) {
        if (strcmp(buffer, head_node->word))
            return true;
            
        head_node = head_node->next;
    }

    return false;
}

 /**
 * Loads dictionary into memory. Returns true if successful else false.
 */
bool load(const char* dictionary)
{
    // Open dictionary file, and error-check
    dict_file = fopen(dictionary, "r");
    if (dict_file == NULL)
        return false;


    while (fgets(buffer, LENGTH+1, dict_file) != NULL) {

        // Temporary reference to the current hash
        hash_index = hash(buffer);

        // Create new node and fill it's word field with the contents of buffer
        head_node = malloc(sizeof(node));
        if (head_node == NULL) {
            printf("malloc returned NULL");
            return false;
        }

        strcpy(head_node->word, buffer);

        if (head_array[hash_index] == NULL)
            head_node->next = NULL;

        else
            head_node->next = head_array[hash_index];

        head_array[hash_index] = head_node;

        wordcount++;
    }

    return true;
}

// Global variables and arrays for simple access
char buffer[LENGTH+1]; // Declares the buffer to store one line or one word in total
int wordcount = 0;
int hash_index = 0;

node* head_array[HASHTABLE_SIZE] = {NULL}; // Stores pointer to node datatype
node* head_node;  // Will always be the most recent node, and first in the list
FILE* dict_file;


 /**
 * Loads dictionary into memory. Returns true if successful else false.
 */
bool load(const char* dictionary)
{
    // Open dictionary file, and error-check
    dict_file = fopen(dictionary, "r");
    if (dict_file == NULL)
        return false;


    while (fgets(buffer, LENGTH+1, dict_file) != NULL) {

    */ REDACTED TO COMPLY WITH ACADEMIC HONESTY /*

    return true;
}

However revised, this is a repost of a now deleted earlier question describing a slightly different issue.

My load() function updates a global array initialized to NULL. check() thereafter converts word to lowercase and stores it in a buffer. Most elements in the array store NULL, however sometimes a real memory address is found and the condition for the while loop, as well as the if condition succeeds and true; gets returned.

My load() function updates a global array initialized to NULL. check() thereafter converts word to lowercase and stores it in a buffer. Most elements in the array store NULL, however sometimes a real memory address is found and the condition for the while loop, as well as the if condition succeeds and true; gets returned.