**Wednesday, Sept.27, 2000**

Hey all!

We have posted three programs since
last week's newsletter.

**Century Sundays** examines
which centuries can (and can't) begin on a Sunday.
If you want the answer, you'll have to check the site. Even there, the
explanation only appears as comments in the source code, or when you
download and run the program. After all, one objective of the site is
to let people see how readable Delphi code is.

**X4X2** is a math oriented
program that proves that for any integer X, if you raise it to the
4th power and subtract the square of the number, the result is always
divisible by 12! No program could prove that this is
true for all integers by examining all integers - too many of them. It
could possibly prove that it's false by a finding single case that is
not true. And if it's true for the first few million integers, you
start to suspect that it's true for all. Fortunately, there
is some not too complicated math reasoning that proves that it's
true for all integers.

**SimpleCalc **is a
prototype 4-function calculator if you're curious about what's
involved. The one posted here took only a few lines of Delphi
code. The final version of this project is being used at Oxford!
I had volunteered to help the Psychology department develop an
on-screen calculator to be used as part of a study of learning by primary
grade school children. The requirements included: 1) display
the user input as well as the result, 2) be shaped to fit across
the bottom of the screen, 3) log user entries to a file with time and
action information, 4) control an MS PowerPoint slide show
presentation, 5) stay on top of the presentation. They say it's
working perfectly (which I doubt). I haven't posted the full source
code because it's kind of specialized but if anyone would have use for
such a program, let me know.

I also wrote a **scientific
function grapher** this week at the request of a teacher looking for
a scientific calculator. It's pretty cool and the initial version has
about 20 lines of Pascal code because it uses a charting component that
comes with Delphi and an open-source downloaded expression parser component. The
20-line version plots polynomials including arithmetic operators, log
and trig functions, etc. It only works for single valued functions of
X though, so it has trouble drawing a circle. The
"final" version solves that problem, includes printing ability,
and allows 2 independent functions to be plotted on the same graph.
Again, it's kind of specialized so I may not post it to the website,
but if anyone is interested send an email.

We're up to 530 hits today.
I'm putting this info in mainly so that I can track usage over time (I'm not
a very organized record keeper).

Gary