Как записать и считать структуру в файл на СИ

Всем добрый вечер, такая проблема, записываю структуру в файл, но при следующем запуске и чтении из файла, программа перестает работать. Также при удаление строчки 114 и 115 программа перестает работать, может кто подсказать почему?

#include <iostream>
#include <iomanip>
#include <cstring>
#include <cstdio>


using namespace std;

typedef struct _date {
    int num;
    char* month;
    int year;
} date;

typedef struct _fio {
    char* fam;      //Фамилия 
    char* name;     //Имя 
    char* father;   //отчество
} fio;

struct _deposid {
    int countName;
    fio client;
    date date;
    double sum;
};

// Функция вывода счета
void printClient(_deposid &client) {
    cout << client.countName << "\t" << client.client.name << "\t" << client.client.fam << "\t" << client.client.father << "\t" << client.date.num << ' ' << client.date.month << ' ' << client.date.year << "\t" << client.sum << endl;
}

void sumLarge(_deposid *clients, int thisClient, int needSum, int countSum) {
    for (int i = 0; i < thisClient; i++ ) {
                    if (clients[i].sum > needSum) {
                        printClient(clients[i]);
                        countSum++;
                    }
                }
                if (countSum == 0) {
                    cout << "The list is empty\n";
                }
                countSum = 0;
}

void printNameLastname(_deposid *clients, int thisClient, char *firstname, char *lastname, char *father, int countSum) {
        for (int i = 0; i < thisClient; i++ ) {
                    if (strcmp(clients[i].client.name, firstname) == 0 && strcmp(clients[i].client.fam, lastname) == 0 && strcmp(clients[i].client.father, father) == 0) {
                        printClient(clients[i]);
                        countSum++;
                    }
                }
                if (countSum == 0) {
                    cout << "The list is empty\n";
                }
                countSum = 0;
}

// Функция создания нового клиента
void newClient(_deposid &client) {
    char *userLastname = new char[100], *userFirstname = new char[100], *userFather = new char[100], *userMonth = new char[100];
    
    // Ввод данных
    cout << "\nInput firstname: ";
    cin >> userFirstname;
    client.client.name = new char[strlen(userFirstname)+1];
    strcpy(client.client.name, userFirstname);
    
    cout << "Input lastname: ";
    cin >> userLastname;
    client.client.fam = new char[strlen(userLastname)+1];
    strcpy(client.client.fam, userLastname);
    
    cout << "Input middlename: ";
    cin >> userFather;
    client.client.father = new char[strlen(userFather)+1];
    strcpy(client.client.father, userFather);
    
    cout << "Input date: ";
    cin >> client.date.num;
    
    cout << "Input month: ";
    cin >> userMonth;
    client.date.month = new char[strlen(userMonth)+1];
    strcpy(client.date.month, userMonth);
    
    cout << "Input year: ";
    cin >> client.date.year;
    
    cout << "\nInput sum on check: ";
    cin >> client.sum;
    
    // Очистка памяти
    delete [] userLastname;
    delete [] userFirstname;
}

int main() {
    char *lastname = new char[100], *firstname = new char[100], *father = new char[100];
    int n, thisClient = 0, numberFunction = 0, needSum, countSum = 0;
    _deposid *clients;
    
    char c;
    FILE *fp;
    fp=fopen("t.txt", "r+");
    if (fp==NULL) {
        fclose(fp);
        fp=fopen("t.txt", "w+");
        cout << "Input amount clients: ";
        cin >> n;
        clients = new _deposid[n]; // Создание массива структур
    }
    else {
        while((c = fgetc(fp)) != EOF) // При удалении этой и строчки ниже программа вообще не запускается
            putchar(c);
        while(fread(clients, sizeof(_deposid),1,fp));
//      fputs("lol", fp);
//      fclose(fp);
    }

    cout << "\n------------------------------------------------\n";
    cout << "Input new check: 1\nOutput all check: 2\nFind all accounts with an amount greater than a given one: 3\nFind all accounts of a given customer (by first and last name): 4\nSave and exit: 5\n";
    
    while (numberFunction != 5) {
        cout << "------------------------------------------------";
        cout << "\nWhat to do: ";
        cin >> numberFunction;
        
        switch (numberFunction) {
            case 1:
                if (thisClient == n) {
                    cout << "\nAdded maximum number of clients";
                } else {
                    clients[thisClient].countName = thisClient + 1;
                    newClient(clients[thisClient]);
                    cout << "\n------------------------------------------------\n";
                    printClient(clients[thisClient]);
                    thisClient++;
                }
                break;
            
            case 2:
                cout << "All check: \n";
                for (int i = 0; i < thisClient; i++ ) {
                    printClient(clients[i]);
                }
                break;
            
            case 3: // Вывод счетов с суммой большей заданной
                cout << "Enter a number to sort: ";
                cin >> needSum;
                cout << "------------------------------------------------\n";
                cout << "Accounts with an amount greater than the specified: \n";
                sumLarge(clients, thisClient, needSum, countSum);
                break;
            
            case 4: 
                cout << "Input firstname: ";
                cin >> firstname;
                cout << "\nInput lastname: "; 
                cin >> lastname;
                cout << "\nInput middlename: "; 
                cin >> father;
                cout << "------------------------------------------------\n";
                cout << "Target customer accounts: \n";
                printNameLastname(clients, thisClient, firstname, lastname, father, countSum);
                break;
            
            case 5:
                cout << "\nSave and exit...";
//              fp=fopen("t.txt","wb");
                for(int i=0;i<n;i++)
                fwrite(&clients, sizeof(_deposid), 1, fp);
                fclose(fp);
        }
    }
}