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Newsletter - August 2000

The ticalc.org Newsletter
August 2000 - Volume 3, Issue 8


Letter from the Editor
Calculator News
Ask ticalc.org
Math Tip
Interview with Steve Whittaker



Wow, lots of new stuff this month for TI calculators. More about that in the Calculator News section of this newsletter. Behind the scenes here at ticalc.org, we've updated our news system so that comment pages are split into parts as they grow large, for users with slower connections. We're currently working on options to allow users specify the number of comments to display at once.

The Program of the Month awards will start up again on ticalc.org. Programs will be selected in four categories: TI-82/TI-83/TI-83+, TI-85/TI-86, TI-89/TI-92/TI-92+, and Computer Utilities/Miscellaneous Programs. All programs released this month that are designated as Featured Programs will be eligible.

This month I've interviewed Steve Whittaker, our local ticalc.org File Archives maintainer.

Thanks for reading the ticalc.org Newsletter!

Eric Sun


As I mentioned before, this was an extremely eventful month in the TI world. First, yet another rom version for the TI-89 and TI-92+, AMS v2.05, was released. You can find more information at http://www.ticalc.org/archives/news/articles/3/38/38694.html.

Many notable programs were also released this month. Probably the most exciting was the release of MirageOS, a new FLASH shell for the TI-83+ created by Detached Solutions. This shell has a huge number of interesting features that we've never seen before on any calculator. Find more information at http://www.ticalc.org/archives/news/articles/3/38/38832.html or visit their web page at http://www.detacheds.com/.

The Doors Team has also released the new version of DoorsOS II. The new version contains some bugfixes and new features. Download it from our archives or visit their home page at http://doors.ticalc.org/.

Until next time...

Eric Sun


At ticalc.org, we often receive many of the same questions. In this column, we hope to address some of these questions for a broader audience. If you'd like to submit a question, please email it to ask@ticalc.org.

Q: I'm worried about the new MirageOS shell writing to the FLASH memory on my TI-83+.

A: MirageOS should be perfectly harmless. As Dan Englender, member of Detached Solutions and one of the chief programmers of MirageOS, said, "We were very conscious about keeping FLASH writes as low as possible, so the only time the the AppVar is written to is the first time you run the application, and when you change options (and it's not even when you change an individual option, it's when you quit the options screen, *if* you've changed any options, that it's rewritten). In addition to that fact, we added an option to MirageOS to allow those of you worried about your FLASH to keep writes to FLASH at near zero. If you go to Miscellaneous Options and uncheck the "Allow Write-Back In Archived Progs" option, no programs will be rewritten to your archive. If you do this, high scores will not be saved in archived programs, but it will *greatly* reduce the number of writes to FLASH, and speed up loading and unloading time." According to TI, it takes about 100,000 erasures of the FLASH memory for the FLASH to wear out. So, you most likely have nothing to worry about running MirageOS on your TI-83+.

Eric Sun


Solving systems of equations is a common task that you are often asked to do in math classes. Usually, the most focus is placed on linear systems of equations. You will undoubtedly be subjected to many techniques that are tedious paper-and-pencil methods. If you have the privilege of using a calculator on a test or homework, you may have wondered if there is an easier way. Indeed, teachers often save calculator methods for the end of the chapter. They also often choose the most inefficient way to do it on the calculator: writing a product equation for the system and solving by computing the inverse. Fortunately for us, the calculator has a much simpler way, rref(). rref stands for Reduced-Row-Echelon-Format. It takes a augmented matrix as its argument. What is an augmented matrix? Well suppose you had a linear system consisting of the equations:

/ 3x + 4y + 2z = 1
| 2x + y + 3z = 0
\ 5x + 4y - 2z = 1

then the augmented matrix would look like:

/ 3 4 2 1 \
| 2 1 3 0 |
\ 5 4 -2 1 /

The solution to this system will be x=a, y=b, z=c where a,b,c are constants to be determined. We often write the solution as an ordered triplet (a,b,c) (or ordered pair in the 2 dimensional case).

To solve this system, we would type the command:

rref([[3,4,2,1][2,1,3,0][5,4,-2,1]]) into our TI calculator, and it would display:

/ 1 0 0 -1/10 \
| 0 1 0 7/20 |
\ 0 0 1 -1/20 /
(the fractions would be decimals if it was not done on TI-89 or TI-92/+)

So our answer is x=-1/10, y=7/20, z=-1/20.

Andy Selle


Email: steve@ticalc.org

Interview Log
Eric How old are you and what level of education do you have?
Steve I'm 15 years old and am going into my sophomore year at Reading Memorial High School in Reading, Massachusetts.
Eric Which calculators do you own?
Steve Both the 86 and the 89. I recieved the 86 as a Christmas present when I was in the 6th grade, and I bought the 89 a little over a year ago.
Eric Do you plan to get any new calculators soon?
Steve I would like a 92+ just to play around with... however, money is a problem, as I don't currently have a job.
Eric How did you get started in the TI community?
Steve I had just recieved my TI-86, and stumbled upon the TI-Files. I saw their IRC information page and thus joined #ti-files on EFnet. Eventually I wound up as an op in #ti, which led to getting a position at ticalc.org.
Eric How long have you been doing archives at ticalc.org?
Steve I've been working on the archives at ticalc.org since the last day of February this year.
Eric How long do you spend working on the ticalc.org archives every week?
Steve When i'm not extremely busy in the week, like I am right now, usually around 1-2 hours a day. It also depends upon how many files are coming in at that time. During school, the time required is much higher as more people are making programs.
Eric What's the best part about working at ticalc.org?
Steve The people, definitely. I've met many people from around the world while working at ticalc that are interested in the same things that I am.
Eric Any bad parts about working at ticalc.org?
Steve Hrrm. That's a tough one. Well, the major part that has been tough for me is incorporating time to the the archives into my schedule. I've been very busy lately and it's been tough to get the archives done. That and the annoying people who email me several times a week asking how to get a calculator on their computer or upload files to the archives. And the first comment posters :). Other than that, it's been great.


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