int x=0;

    while(true){
        cout<<"Menu"<<endl;
        cout<<"1. Add student"<<endl;
        cout<<"2. Delete student"<<endl;
        cout<<"3. Show student data"<<endl;
        cout<<"4. Update student data"<<endl;
        cout<<"5. Show all student data"<<endl;
        cout<<"6. Quit"<<endl;
        cout<<"Wybieram : ";
        cin>>x;
        system("cls");
        switch (x)
        {
            case 1:
                string name,surname,fieldOfStudy;
                int age,indexNr,birthDay,birthMonth,birthYear;
                float avarageGrade;
                cout<<"Adding a new student"<<endl;
                cout<<"Give student data"<<endl;

                cout<<"Name:";
                cin<<name;

                cout<<"Surname:";
                cin<<surname;

                cout<<"Birth:"<<endl;

                cout<<"Year:";
                cin<<birthYear;
                cout<<"Month:";
                cin<<birthMonth;
                cout<<"Day:";
                cin<<birthDay;

                cout<<"Age:";
                cin<<age;

                cout<<"Index Number:"
                cin<<indexNr;

                cout<<"Field of Study:";
                cin<<fieldOfStudy;

                cout<<"Avarage grade:";
                cin<<avarageGrade;

                addStudent(name,surname,birthDay,birthMonth,birthYear,age,fieldOfStudy,indexNr,avarageGrade);

                break;
            case 2:
                int indexNr;
                cout<<"Removing a student"<<endl;
                cout<<"Give student index to delete data."<<endl;
                cin<<indexNr;
                removeStudent(indexNr);
                break;
            case 3:
                int indexNr;
                cout<<"Viewing student data"<<endl;
                cout<<"Give student index to show data."<<endl;
                cin<<indexNr;
                printStudent(indexNr);
                break;
            case 4:
                string name,surname,fieldOfStudy;
                int age,indexNr,birthDay,birthMonth,birthYear;
                float avarageGrade;
                cout<<"Editing a student"<<endl;
                cout<<"Give student data"<<endl;

                cout<<"Name:";
                cin<<name;

                cout<<"Surname:";
                cin<<surname;

                cout<<"Birth:"<<endl;

                cout<<"Year:";
                cin<<birthYear;
                cout<<"Month:";
                cin<<birthMonth;
                cout<<"Day:";
                cin<<birthDay;

                cout<<"Age:";
                cin<<age;

                cout<<"Index Number:"
                cin<<indexNr;

                cout<<"Field of Study";
                cin<<fieldOfStudy;

                cout<<"Avarage grade:";
                cin<<avarageGrade;

                updateStudent(name,surname,birthDay,birthMonth,birthYear,age,fieldOfStudy,indexNr);
                break;
            case 5:
                string field;
                cout<<"Viewing all students data"<<endl;
                cout<<"Field of study:"
                cin<<field;
                printAllStudentsOfField(field);
                break;
        }
        if(x==6)
            break;
    }