public class student
    {
        public string strname;
        private int nage;
        public void setage(int _nage)
        {
            this.nage = _nage;
        }
        public int getage
        {
            return this.age;
        }
    }
    class Class1
    {
        static void main(string[] args)
        {
            student s=new student ();
            s.setage(20);
            Console.WriteLine(s.getage);
        }
    }
这程序中“public class student” 和“class Class1
”什么意思

谢谢