Implementing Abstract class In C#

using System;
abstract class person {
    protected string fname;
    protected string lname;
    public person(string fn, string ln) {
        fname = fn;
        lname = ln;
    }
    public virtual void display() {
        Console.WriteLine("Person :" + fname + " " + lname);
    }
}
class emp: person {
    public ushort year;
    public emp(string fn, string ln, ushort yr): base(fn, ln) {
        year = yr;
    }
    public override void display() {
        Console.WriteLine("Employee :" + fname + " " + lname + " " + year);
    }
}
class worker: person {
    public String company;
    public worker(string fn, string ln, string c): base(fn, ln) {
        company = c;
    }
    public override void display() {
        Console.WriteLine("Worker :" + fname + " " + lname + " " + company);
    }
}
class Program {
    static void Main(string[] args) {
        Console.WriteLine("**ABSTRACT CLASS **");
        person p2 = new emp("Vijay", "Senthil", 2012);
        person p3 = new worker("Vijay", "Senthil", "C Sharp Corner");
        p2.display();
        p3.display();
        Console.ReadKey();
    }
}