What's New?

• The Future?

  The rapid increase in the use of mobile devices (such as the iPad) with browsers that do not run Java Applets has raised questions about the future of Jack's Page. As I write this I have Leonard Cohen's The Future CD playing, and as he says I've seen the future, brother: it is murder. The same may be said about the CD itself: I could play it in the CD changer in my 2007 VW, but my 2011 VW has no CD player of any kind. When Apple announced a move into the textbook market for the iPad, I hoped that might mean Applet support, but no such luck. With this as background, you can see why I didn't introduce much new material this season (ending 29 March 2012). I'll have to see what the future looks like in the Fall.

• Java Instructions

  On 9 Feb 2012 I tried to follow my Java Instructions. I did this because my grandson Ryan (in his early twenties) is coming for a visit, and I want to see what he thinks of the instructions. I was horrified to find that none of my internal links worked because the sample program had been revised and even its name had been changed. I have fixed things so that I can follow the instructions on my local copy of Jack's Page, but the final verdict will come from Ryan working with the web version. My apologies to anyone who tried to follow the posted instructions and ran into a brick wall (I doubt that I am apologizing to many people).

• Two or Three Interacting Bodies

  On 19 Jan 2012 I uploaded a revision of the section on the two-body problem that includes the option of adding a third body. This acts as a bridge to the section on the restricted three-body problem (the Trojan Asteroids).

• The Simple Pendulum

  I thought I should do something to balance out the arcane posting on Transient Analysis (below), so I uploaded a section on The Simple Pendulum on 6 Dec 2011. It deals with the amplitude-dependence of the period of oscillation.

• Transient Analysis

  On 30 Oct 2011 I uploaded a revised version of the Logarithmic Transient Applet. It takes account of the field-dependence of the dielectric constant during an open-circuit transient.

• Java 6

  On 17 Feb 2011 I uploaded versions of the 74 Java class files on Jack's Page produced using the Java 6 compiler. Previously I had used versions produced by the Java 3 compiler because they ran on my old notebook computer, and a few programs ran 9 times faster in Java 3 than in Java 6. (I have rewritten these programs to eliminate the speed difference, and I no longer have the old notebook). The BASIC program revisions (below) involve revision of the Java source code also, so this seemed to be an appropriate time to switch to Java 6. It simplifies my development work because I have already been forced to use the Java 6 appletviewer to avoid conflicts with Windows Vista and Windows 7.

• BASIC Programming Languages

  On 31 January 2011 Jack's Page contained 73 Applets with Java source code and corresponding programs written in BASIC. There were 70 programs written in Liberty BASIC and 34 written in BBC BASIC. After the revisions uploaded on 20 March 2011, each Applet has only one corresponding BASIC program. 47 are written in BBC BASIC and 26 in Liberty BASIC. I no longer plan to eliminate all Liberty BASIC programs, but those that remain will have to be revised to deal with the idiosyncrasies of the various versions of Windows.

  The 11 PostScript programs will be retained along with 1 Fortran and 1 HP48 program. Initially PostScript and HP48 were used to show that the algorithms could be implemented on devices as different as printers and calculators. (At present I use PostScript to produce hard copy of what an applet displays on the screen). The Fortran listing shows how much simpler programs appear when the language can deal with complex variables. The HP48 calculator, although too slow to be of use today, treats variables as complex by default, and has a stack structure similar to that of PostScript.