Вывести список учеников и год их рождения, фамилия которых начинается с указанной буквы, указанного года рождения

#include <iostream>
#include <Windows.h>
#include <sstream>
#include <string>
#include <xstring>
#include <time.h>
 
using namespace std;
 
class student
{
private:
    string surname = ""; char address = 'a'; int yearofborn = 0, phonenumber = 0;
public:
    student() {}
    void set(string Surname, char Address, int Yearofborn, int Phonenumber)
    {
        surname = Surname; address = Address; yearofborn = Yearofborn; phonenumber = Phonenumber;
    }
    string getallinfo()
    {
        stringstream info;
        info << "Surname: " << surname << " Address: " << address << " Year of born: " << yearofborn << " Phone number: " << phonenumber; 
        return info.str();
    }
    bool issurnamestartedbythissymbol(char a) { if (surname[0] == a) return true; else return false; }
    bool isphonenumber(int a) { if (phonenumber == a) return true; else return false; }
    bool isyearofborn(int a) { if (yearofborn == a) return true; else return false; }
    bool isaddress(char a) { if (address == a) return true; else return false; }
};
 
int main()
{
    srand(time(NULL));
    student students[30];
    for (int i = 0; i < 30; i++) 
    { 
        string surname = "";
        surname += char(97 + rand() % 25);
        surname += char(97 + rand() % 25);
        surname += char(97 + rand() % 25);
        students[i].set(surname, char(97 + rand() % 25), 2000 + rand() % 10, rand() % 100);
    }
    for (int i = 0; i < 30; i++)
        cout << students[i].getallinfo() << endl;
    char symbol = 'a';
    cout << endl;
    for (int i = 0; i < 30; i++)
        if (students[i].issurnamestartedbythissymbol(symbol)) cout << students[i].getallinfo() << endl;
    char year = 2005;
    cout << endl;
    for (int i = 0; i < 30; i++)
        if (students[i].isyearofborn(year)) cout << students[i].getallinfo() << endl;
    symbol = 'b';
    cout << endl;
    for (int i = 0; i < 30; i++)
        if (students[i].isaddress(symbol)) cout << students[i].getallinfo() << endl;
    int numb;
    cout << "\nPhone number "; cin >> numb;
    cout << endl;
    for (int i = 0; i < 30; i++)
        if (students[i].isphonenumber(numb)) cout << students[i].getallinfo() << endl;
    return 0;
}