I am trying to prepare a database using C,which can store data and from which data can be retrieved and edited.
First storing,then retrieving data from the file works.But,during first run of the prog if choice#2(i.e.,DISPLAY)is entered without entering any data using choice#1(although the file contains data),then error occurs,gets hung.A part of the prog is shown:

#

include<stdio.h>
#include <string.h>
#include <conio.h>
#include <stdlib.h>typedef struct {
  char name[30];
  char company[50];
  char address[200];
  char pin[7];
  char web[30];
  }entry;
FILE *fpt;int menu(void);
entry *ptr,commodity;
int n=sizeof(entry);
void main()
{
 int choice;
 do
 {
 choice=menu();
 switch(choice)
 {
  case 1:ptr=(entry *)malloc(sizeof(entry));
   fpt=fopen("data4.bin","a");
   printf("\nEnter the name of the commodity:");
   scanf("%s",ptr->name);
   printf("\nEnter the name of the producing company:");
   scanf("%s",ptr->company);
   printf("\nEnter the address of the producing company:");
   scanf("%s",ptr->address);
   printf("\nEnter the pincode:");
   scanf("%s",ptr->pin);
   printf("\nEnter the website of the producing company:");
   scanf("%s",ptr->web);
   fwrite(ptr,n,1,fpt);printf("ENTERED\n");
   fclose(fpt);
   continue;
  case 2:fpt=fopen("data4.bin","r");
         
     do 
     {
     if (fread(&ptr->name, sizeof(ptr->name), 1, fpt) == 1 &&
       fread(&ptr->company, sizeof(ptr->company), 1, fpt) == 1 &&
       fread(&ptr->address, sizeof(ptr->address), 1, fpt) == 1 &&
       fread(&ptr->pin, sizeof(ptr->pin), 1, fpt) == 1 && 
       fread(&ptr->web, sizeof(ptr->web), 1, fpt) == 1)
         {
         printf("\n\nThe name of the commodity:");
      printf("%s",ptr->name);
      printf("\nThe name of the producing company:");
      printf("%s",ptr->company);
      printf("\nThe address of the producing company:");
      printf("%s",ptr->address);
      printf("\nPincode:");
      printf("%s",ptr->pin);
      printf("\nWebsite of the producing company:");
      printf("%s",ptr->web);
        }
   else if (feof(fpt)) 
          {
    printf("\n\nfinished reading file!\n");
    break;
    }
   else {
    printf("an error occured while reading the file!\n");
    break;
    }
} while (1);
         fclose(fpt);continue;
    case 3:printf("\nThank You for using!");exit(1);              
 }
 }while(choice==1||choice==2);
 getch();
}
int menu(void)
{
 int choice;
 do{
  printf("Enter your choice:\n");
  printf("1.CREATE the linked list\n");
  printf("2.DISPLAY\n");
  printf("3.EXIT\n");
  scanf("%d",&choice);
 }while(choice!=1 && choice!=2 && choice!=3);
 return(choice);
}

Please suggest the cause of this error!

Thanks a lot Mr.dilip.mathews,your suggestion helped me to correct my prog.Now it is working.

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