Writing Structure to data file

Following program will declare a Structure "customer". Program reads customer information and then writes into a "customer.dat" file.

#include <stdio.h>
//Define structure to store customer data.
struct customer
{
   char fname[30];
   char lname[30];
   int  ac_num;
   float ac_balance;
};

void main ()
{
   FILE *fp;
   //declare structure(customer) variable
   struct customer input;
   // open customer file for writing
   fp = fopen ("customer.dat","w");
   if (fp == NULL){
      printf("\nFile opening error..\n\n");
      exit (1);
     }

   printf("Enter \"exit\" as First Name to stop reading user input.");

   while (1)
     {
      printf("\nFirst Name: ");
      scanf ("%s", input.fname);
     
      if (strcmp(input.fname, "exit") == 0)
         exit(1);
     
      printf("Last Name : ");
      scanf ("%s", input.lname);
      printf("Account Number  : ");
      scanf ("%d", &input.ac_num);
      printf("Balance   : ");
      scanf ("%f", &input.ac_balance);

      // write customer data to customer.dat  file
      fwrite (&input, sizeof(struct customer), 1, fp);
     }
}

Output of program

Enter "exit" as First Name to stop reading user input.
First Name: ABC
Last Name : PATEL
Account Number  : 101
Balance   : 55000

First Name: XYZ
Last Name : SHAH
Account Number  : 102
Balance   : 50000


First Name: exit