Saving data in files in c - c

Question

I am working on this cinema reservation project !! 2 problems i m facing here is with data saving.
1) : when i close the program and try to register a new user the login information of previous registered user deletes Even though i am opening file in "a+" mode. but if i directly log in with the already registered user it works. the thing is i am not able to register more than 1 user at a time.
2) : When i close the program and logged in again the information of user reservation deletes. i want to save the user's reservation information too.
How can I solve this ?
struct login
{
char fname[100];
char lname[100];
char username[20];
char password[20];
};
#include <stdio.h>
#define RVALUE 5
#define CVALUE 10
int i, j;
void DisplaySeats(void);
void ReserveSeats(void);
void ChooseSeat(void);
void CancelSeat(void);
void CheckCancelSeat(void);
void menu(void);
int Seats[RVALUE][CVALUE];
void registration();
void login();
int main()
{
int c;
int choice, menu;
printf("Welcome to our small Cinema!!!\n");
printf("\n");
//DisplaySeats();
printf("\n1 : register!!!\n");
printf("2 : login!!!\n");
printf("3 : quit\n");
printf("Enter your choice : \n");
scanf("%d",&c);
switch (c)
{
case 1:
registration();
break;
case 2:
login();
break;
case 3:
printf("Thankyou for Choosing our small Cinema !! \n");
getch();
exit(1);
default :
system("CLS");
printf("Enter a valid number !!\n");
main();
}
getch();
}
void registration()
{
FILE *log;
log = fopen("login.txt", "a+");
struct login l;
printf("\nEnter first name : ");
scanf("%s", &l.fname);
printf("\nEnter last name : ");
scanf("%s", &l.lname);
printf("\nEnter your Username : ");
scanf("%s", &l.username);
printf("\nEnter your password : ");
scanf("%s", &l.password);
fwrite(&l, sizeof(l), 1, log);
fclose(log);
printf("\nYou are successfully registered!!");
printf("\nYour UserId is %s and your password is %s", l.username, l.password);
printf("\nNow login with your username and password!!");
printf("\nPress any key to continue ...");
getch();
system("CLS");
main();
}
void login()
{
char username[100];
char password[100];
FILE *log;
struct login l;
log = fopen("login.txt", "r");
if (log == NULL)
{
printf("FILE NOT FOUND!!!");
exit(1);
}
printf("\nUserID : ");
scanf("%s", &username);
printf("\nPassword : ");
scanf("%s", &password);
while (fread(&l, sizeof(l), 1, log));
{
if (strcmp(username, l.username) == 0 && strcmp(password, l.password)==0)
{
system("CLS");
printf("\nYou are successfully logged in !!\n");
menu();
}
else
{
printf("\nYour UserID or password is incorrect !!\n");
printf("Press any key to continue ...\n");
getch();
system("CLS");
login();
}
}
fclose(log);
}
void ChooseSeat(void)
{
int row, col,k;
printf("Which row do you want to choose? : ");
scanf("%d", &row);
printf("Which seat do you want to select? : ");
scanf("%d", &col);
if (row > RVALUE || col > CVALUE)
{
printf("Wrong Entry !! Try again\n");
ChooseSeat();
}
else if (Seats[row - 1][col - 1] != 0)
{
printf("Seat is already reserved try again !!\n");
ChooseSeat();
}
else
{
Seats[row - 1][col - 1] = 1;
printf("Congratulations!! Reservation Completed!!!\n");
DisplaySeats();
printf("\nPress any key to go to main menu!!");
getch();
system("CLS");
main();
}
}
void ReserveSeats(void)
{
int NoOfSeats,i;
printf("How many seats do you want to reserve?\n");
scanf("%d", &NoOfSeats);
DisplaySeats();
for (i = 1; i <= NoOfSeats; i++)
{
ChooseSeat();
}
}
void DisplaySeats(void)
{
printf("\t \t Seats\n");
printf("\t 1 2 3 4 5 6 7 8 9 10\n");
for (i = 0; i < RVALUE; i++)
{
printf("Rows %d : ", i + 1);
for (j = 0; j < CVALUE; j++)
printf("%d ", Seats[i][j]);
printf("\n");
}
printf("\n");
}
void CheckCancelSeat(void)
{
while (1)
{
for (i = 0; i < RVALUE; i++)
{
for (j = 0; j < CVALUE; j++)
{
if (Seats[i][j] == 0)
{
printf("There is no reserved seat available!!\n");
break;
}
else
{
CancelSeat();
}
break;
}
break;
}
system("CLS");
break;
}
}
void CancelSeat(void)
{
int r, c;
printf("\nWhich row do you want to cancell ? : ");
scanf("%d", &r);
printf("\nWhich column do you want to cancell ? : \n");
scanf("%d", &c);
if (Seats[r - 1][c - 1] != 0)
{
Seats[r - 1][c - 1] = 0;
printf("Your Seat is Cancelled !!\n");
system("CLS");
}
else
{
printf("Wrong Entry !!\n");
CancelSeat();
}
}
void menu(void)
{
int choice;
DisplaySeats();
printf("1 : reserve a seat\n");
printf("2 : cancell a seat\n");
printf("3 : Main Menu\n");
printf("Enter your choice : \n");
scanf("%d", &choice);
system("CLS");
switch (choice)
{
case 1:
ReserveSeats();
break;
case 2:
CheckCancelSeat();
break;
case 3:
main();
break;
default:
printf("Please enter a valid choice!!");
menu();
break;
}
}

Answer 1

The problem is that it is very difficult to save more than one structure to a binary file.
Note: Binary files do not have the file extension ".txt" but z. ".Bin", ".dat" or the like; Sometimes binary files are saved even without file extension.
I think you try to "spam" the password in the binary file (encrypt). Unfortunately, I have to tell you that this does not work. If you open the file with a text editor you will see the password.
I would suggest you save the data as a text file and then read the data step by step.
Also, you did not have all the functions declarated.
There are implicit declarations. This can lead to errors for larger programs. For a few, the solution would be to include stdlib.h.
If you want to save a file the following night please use the mode Subfix "b" z. Eg "a + b".
A few helpful links are possible:
http://www.cplusplus.com/reference/cstdio/fopen/
http://www.cplusplus.com/reference/cstdio/fwrite/
Reading/Writing a structure into a binary file
Although I could not solve the problems, but I hope I could help anyway.
If you still want to save the structures in a binary file, you can read this on the Internet (I just say Google).
For example, if you want to encrypt something with C, you can search for a crypt library or something similar.