Adding Students to a database

Im trying to add users to a student database.

When i try to add it lets me enter 4 of 5 items then crashes.

Any ideas?

Code below:

Code:

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#include <iostream.h>
#include <conio.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>

#define NO_OF_STUDENTS 20

struct student_type
{
                char  reg[20];
                char  surname[25];
                char  firstname[25];
                char  phone;
                int  credit;
};

void    initialise_data(student_type[]);
void            add_car(student_type[]);
void      show_all_cars(student_type[]);
void          save_data(student_type[]);
void            show_car(student_type[], int);


void main()
{
        student_type  cars[NO_OF_STUDENTS];
        char choice;
                                            // Load car file into database
        initialise_data(cars);
                                      // Display menu and get user choice
        do
        {
                cout << "\n\n"
                          << "\nAdd a Student \t\t\tA"
                          << "\nShow all Students \t\tS"
                          << "\nFind a Student \t\t\tF"
          << "\n        Quit \t\t\tQ"
          << "\n\nChoice:- ";
                cin  >>  choice;
      choice = toupper(choice);

                switch (choice)
                {
                        case 'A':
                                                add_car(cars);
                                                break;
              case 'S':
                                                show_all_cars(cars);
                                                break;
                }
        } while (choice != 'Q');
}


void initialise_data(student_type cars[])
                                      // Loads car database from file
{
        int i, count = 0;
        FILE *in_file;

        for (i = 0; i < NO_OF_STUDENTS; i++)
                cars[i].phone = 0;

        in_file = fopen("cars.dat", "rb");

        if (in_file == NULL)
            cout << "Starting a new data file\n";
        else
                                              // If the file did open - read the data
                                              // After this 'count' will contain the
                                    // number of car records read.
                count = fread(cars, sizeof(student_type), NO_OF_STUDENTS, in_file);

        fclose(in_file);

        cout << "\nNo of Students on file is " << count;
}

void add_car(student_type cars[])
                                                                                        // Create a new car record in the database
{
        int next;


                                  // Count how many cars already in database
        for (next = 0; next < NO_OF_STUDENTS && cars[next].phone > 0; next++);

        if (next < NO_OF_STUDENTS)        // If database is not full, add a car
        {
                cout << "\nRegistration Number:  ";
                cin  >> cars[next].reg;
                cout <<  "Surname: ";
                cin  >> cars[next].surname;
                cout <<  "First Name:    ";
                cin  >> cars[next].firstname;
                cout <<  "Phone:  ";
                cin  >> cars[next].phone;
                cout <<          "Credits:  ";
                cin  >> cars[next].credit;
        }
        else                          // If database is full, give message
                cout << "No room for any more Students\a\n";
                                      // Database has changed so save it
        save_data(cars);
}

void show_car(student_type cars[], int position)
                                  // Display any car knowing its array position
{
        cout << "\n\nRegistration Number:-  " << cars[position].reg;
        cout <<  "\nSurname:- " << cars[position].surname;
        cout <<  "\nFirst Name:-  " << cars[position].firstname;
    cout <<  "\nPhone:-  " << cars[position].phone;
        cout <<          "\nCredits:-  " << cars[position].credit;
}

void show_all_cars(student_type cars[])
                                  // Display all cars by calls to show_car()
{
  for (int i = 0; i < NO_OF_STUDENTS && cars[i].phone > 0; i++)
                show_car(cars, i);
}

void save_data(student_type cars[])
                                  // Save database to disk after each change
{
        FILE *out_file;
        int i;

        out_file = fopen("cars.dat", "wb");

        for (i = 0; i < NO_OF_STUDENTS && cars[i].phone > 0; i++)
                fwrite(&cars[i], sizeof(student_type), 1, out_file);

        fclose(out_file);
}

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Well step 1 is read the forum anouncements and use [code][/code]Tags

sorry about that, fixed it

I didn't have any problems adding students. However, when you save, be sure to save your count first since you're expecting this when you load the file.

Code:

---

void save_data(student_type cars[])
                                  // Save database to disk after each change
{
        FILE *out_file;
        int i;

        out_file = fopen("cars.dat", "wb");

        // Write out the number of students

        for (i = 0; i < NO_OF_STUDENTS && cars[i].phone > 0; i++)
                fwrite(&cars[i], sizeof(student_type), 1, out_file);

        fclose(out_file);
}

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In addition, you probably want to change the void main to an int main, since you'll be bugged about that 'til kingdom come. Also, you may want to change this:

Code:

---

#include <iostream.h>
#include <conio.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>

---

to this:

Code:

---

#include <iostream>
#include <stdio.h>
/*
#include <conio.h> //nothing used from this one
#include <ctype.h> //or this one
#include <string.h> //or this one
*/

using std::cout;
using std::cin;

---

<iostream.h> is a deprecated header file. <iostream> is the same thing except everything is in the std namespace instead of the global namespace.

You could also consider using a struct to hold the count and your array, since you don't really need to compute the count.

Code:

---

struct student_db_type
{
        student_type cars[NO_OF_STUDENTS];
        int count;
};

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Load the count from the file, and then just increment the count when you add a record, and your count will be up-to-date.