Notes: Tuesday 26 November 2002

Schedule

• 4 December (11:59pm): Problem Set 7 (code submission)
• 5 December (beginning of class): Problem Set 7 (turnin)
• The final exam will be handed out 5 December, due date TBA. The final will be "optional" — it will either replace a previous exam grade or count as extra credit, but cannot count against you. When Exam 2 is returned next week, you will get some guidance that will help you decide whether or not you should do the final.

Notes

What different kinds of abstraction have we seen in CS201J?

What is Computer Science?

What properties are necessary for a game to have a meaningful championship?

Measuring Networks

Latency — Time from sending a bit until it arrives seconds (or seconds per geographic distance)

Bandwidth — how much information can you transmit per time unit bits per second

Here is some code you may find useful for PS7:

import java.io.*;
import java.net.*;

public class MySnake extends SnakeInterface {
    ... 

    public MySnake (Socket s) throws IOException {
	super (s);	
	... 
    }

    public void updateState () {
	if (display != null) {
	    display.updateGrid ();
	}
    }

    static public void main (String args[]) {
	if (args.length != 2) 
	    {
		System.err.println ("Usage: java MySnake  ");
		System.exit (1);
	    } 
	else
	    {
		String server = args [0];
		int port = Integer.valueOf (args[1]).intValue ();

		try {
		    Socket s = new Socket (server, port);
		    MySnake ms = new MySnake (s);
		} catch (UnknownHostException e) {
		    System.err.println ("Cannot find host: "+ server);
		    System.exit (1);
		} catch (IOException e) {
		    System.err.println ("Unable to open connection to " + server + ": " + e);
		    System.exit (1);
		}
	    }
    }
}

Links

• CS200 Web Site
• The Early History of Data Networks, Gerard J Holzmann and Björn Pehrson.
• A Brief History of the Internet
• Hobbe's Internet Timeline
• A Paternity Dispute Divides Net Pioneers, New York Times, 8 November 2001. (Fighting over who deserves credit for inventing packet switching).
• Al Gore and the Internet, Robert Kahn and Vinton Cerf.

University of Virginia Department of Computer Science CS 201J: Engineering Software

Sponsored by the National Science Foundation

cs201j-staff@cs.virginia.edu