Opinion's of Small program

[Arthur]

Hi I am a beginner learning C and welcome opinion / constructive criticism of a phone book program I wrote. If it is legible, needs comments, makes sense , just done plain old wrong 🙂

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct Contact{
   char name[15];
   char surname[15];
   char number[15];
}entry;

int const SIZE = 22;
int count;
entry *book;
FILE *store;

int open_store(char *mode){
   store = fopen("store.dat", mode);
   if (store == NULL){
      return 1;
   }
   return 0;
}

void rewrite_store(){
   int index;
   open_store("w");
   for (index = 0; index < count; index++){
      fprintf(store, "\n%s\t%s\t%s", book[index].name, book[index].surname, book[index].number); 
   }
   fclose(store);
}

void load_book(){
   while(fscanf(store, "%s", book[count].name) == 1){
      fscanf(store, "\t%s\t%s\n", book[count].surname, book[count].number);
      count++;
   }
}

void print_book(){
   int loop = count;
   int index = 0;
   while (loop > 0){
      printf("#-%d:%s %s:%s\n", index,  book[index].name, book[index].surname, book[index].number);
      loop--;
      index++;
   }
}

void sort_book(){
   int index, index_1, index_2;
   for(index_1 = 0; index_1 < count; index_1++){
      for(index_2 = index_1 + 1; index_2 < count; index_2++){
         if (strcmp(book[index_1].surname, book[index_2].surname) > 0){
            book[count + 1] = book[index_1];
            book[index_1] = book[index_2];
            book[index_2] = book[count + 1];
         }
      }
   }
   book[count + 1] = book [count + 2];
   rewrite_store();
}

void search(){
   char temp [15];
   int index;
   int bin_index = 0;
   int bin[10];
   printf("Enter last Name:");
   scanf("%s", temp);
   for (index = 0; index < count + 1; index++){
      if (strcmp(temp, book[index].surname) == 0){
         bin[bin_index] = index;
         bin_index++;
      }
   }
   if (bin_index > 0){
      int i;
      for (i = 0; i < bin_index; i++){
         printf("#-%d:%s %s:%s\n",bin[i], book[bin[i]].name, book[bin[i]].surname, book[bin[i]].number);
      }
   }
}

void new_entry(){
   if (count > SIZE - 3){
      printf("Phone Book Full\n");
      return;
   }
   printf("First Name:");
   scanf("%s", book[count].name);
   printf("Last Name:");
   scanf("%s", book[count].surname);
   printf("Number:");
   scanf("%s", book[count].number);
   count++;
   rewrite_store();
}

void delete_entry(){
   int select;
   int confirm;
   print_book();
   printf("Enter Index # To Delete:");
   scanf("%d", &select);
   printf("Delete #- %d:%s %s:%s\n", select, book[select].name, book[select].surname, book[select].number);
   printf("ReEnter Index # To Confirm:");
   scanf("%d", &confirm);
   if (confirm == select){
      int i;
      for (i = select; i < count; i++){
         book[i] = book[i + 1];
      }
      count--;
      rewrite_store();
   }
}

int menu(){
   int selection;
   printf("\nMENU\n");
   printf("EXIT - 9       \tShow All-1    \tAdd New - 2\n");
   printf("Sort - 3       \tSearch - 4    \tDelete Contact - 5\n");
   scanf("%d", &selection);
   switch (selection){
      case 1:
         print_book();
         return 1;
      case 2:
         new_entry();
         return 1;
      case 3:
         sort_book();
         return 1;
      case 4:
         search();
         return 1;
      case 5:
         delete_entry();
         return 1;
      case 9:
         break;
      default:
         break;
   }
   return 0;
}

int main(){
   book = (entry*) malloc(sizeof(entry)* SIZE);
   int state = 1;
  
   state = open_store("r");
   if (state == 1){
      state = open_store("w");
      fclose(store);
      state = open_store("r");
   }
   if (state == 1){
      printf("Error Opening Phone Book");
      return 0;
   }
   load_book();
   fclose(store);
   state = 1;
   printf("*******Phone Book*******\n");
   while (state == 1){
      state = menu();
   }
   free(book);
   return 0;
}