This is a c programme to count the frequency of each word in a file

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct words
{
    char *word;        //struct words is a binary tree that stores a node and a pointer to the left and right siblings
    int count;
    struct words *left;
    struct words *right;
};
struct words *bintree(struct words **head,char *word);//bintree is a function of type struct words and the 1st arg is a pointer to the bin tree that stores the words
void print_tree(struct words *head);//print_tree is a function that prints a binary tree
char *readfile(char *filename);//readfile is a function that reads a text file and stores it in a string
int total;//an interger to store the total number of words in the file
int
main (int argc, char *argv[])
{
    char *word=NULL,*str=NULL;
    total = 0;
    struct words *head=NULL;
   
    if((str = readfile(argv[1])) != NULL)//
    {
       
        const char* delim = " ,\n\r\t.;:_-()~`|!?><%^&*$#@{}[]0123456789\'\"/";//delim is list of all chars that seperates two words form each other
        word = strtok(str,delim);//strtok is takes a string and seperates it into words using the delimities
        head = bintree(&head,word);
        while((word = strtok(NULL,delim)) != NULL){
            head = bintree(&head
            ,word);
        }
        printf("Total = %d\n",total);
        printf("|%-20s | %-5s |\n%25s\n","WORDS","freq","|============================");
        print_tree(head);
    }
    return 0;
}


void print_tree(struct words *head){
    if(head == NULL)
        return ;
    print_tree(head->right);//note that print_tree uses the post order traversal to print the tree
    printf("|%-20s | %-5d |\n",head->word,head->count);
    print_tree(head->left);
    return ;   
}
char *readfile(char *filename){
    FILE *fp = fopen(filename,"r");
    char *str=NULL;
    if(fp !=NULL){
        fseek(fp,0,SEEK_END);//moves the pointer 2 the end of the file
        long int size = ftell(fp);//ftel determine the size of the file
        rewind(fp);//rewind brings the pointer back to te beginning
        str = malloc(size + 1);
        fread(str,size,1,fp);//fread read the the entire file and stores it in a file.the 1 signifies it is reading the entire file as one block
        fclose(fp);
    }
    return str;
}

struct words *bintree(struct words **head,char *word){
    if(*head == NULL){
        *head = malloc(sizeof(struct words *));//allocate space for the words
        (*head)->word = malloc(sizeof(char) * strlen(word) + 1);
        strcpy((*head)->word,word);
        (*head)->count = 1;
        (*head)->left = (*head)->right = NULL;
        total++;
    }
    else if(strcasecmp((*head)->word,word) < 0){//strcasecmp compares without considering the cases
        bintree(&(*head)->left,word);
    }
    else if(strcasecmp((*head)->word,word) > 0){
        bintree(&(*head)->right,word);
    }
    else{
        (*head)->count++;
        total++;
    }
   
    return *head;
}