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Newsletter - November 1998 Newsletter

The ticalc.org Newsletter
November 1998 - Volume 1, Issue 1


Letter from the Editor
Calculator News
Graphing Piecewise Functions
Interview with Brett Barwick
Subscribing and Unsubscribing Information
Web Archive


Thank you for reading the ticalc.org newsletter! This newsletter has recently undergone some changes. I, Kirk Meyer, have become the editor, and it has been changed from a weekly newsletter to a monthly newsletter. Because of this change, the program of the week award has been eliminated, and the program of the month awards will begin in January. If you have anything that you would like to have published in this newsletter, please send it to newsletter@ticalc.org.

Each month I will print one letter that I choosein a "Letter to the Editor" section. You can send letters regarding just about anything as long as they are constructive. Send your letters to the editor to newsletter@ticalc.org.

Kirk Meyer


In ticalc.org news, two new staff members have been added: Kirk Meyer, and Ahmed El-He lw. I am in charge of maintaining the recently overhauled Reviews section and also of editing this newsletter. Ahmed is in charge of maintaining the new Program Ideas and Upcoming Programs sections. Additionally, The TI-Files, a major competitor of ticalc.org, acquired their own domain name. They are only the second TI calculator site to do so.

In other news, two programming alliances have been formed. The ACZ (Assembly Coders Zenith) and Z80 Assembly Coders. The ACZ consists of CLEM, Dux Gregis, JBrett, David Phillips, and Dave Scheltema. The Z80 Assembly Coders consists of Will Dempster, InFuZeD, Ian Kaplan, and Jesse Keane. I retired from programming calculators and released all of my source code to the public.

New programs of note include SOS v1.6, Doors OS v0.8 Beta (for the TI-89 and the TI-92 Plus), and Crash v1.5. Texas Instruments has released the original TI-89 Flash ROM to the public as well as Flash ROM upgrades to the TI-73 and the TI-92 Plus.


This month I have decided to write an article about how to graph piecewise functions on nearly any TI graphing calculator (although I haven't tried it on all of them). One caveat before you start: you will not be able to calculate derivatives of piecewise functions or draw tangent lines. Most other functions should work including integration. First I will start by saying how this works. When the TI tests a condition, it returns 1 if it is true and 0 if it is false. So if you multiply a condition by an expression that expression will appear only if the condition is true.

With that in mind, here is how to graph piecewise functions. Suppose you have y=x for x less than zero and y=x+1 for x greater than or equal to zero. You would enter this as y1=(x<0)(x)+(x>=0)(x+1). Simply multiply each condition by its corresponding function and add them all together. You can have as many pieces as you want with this method and it will still be treated as one function (except for derivatives). Notice that this will work for all kinds of graphs, not just functions. It will work for polar (with a condition on theta), parametric (with a condition on t), etc. I hope this is useful for you in some math class along the way!


Email: tbarwick@esn.net
ICQ UIN: 20607010

Interview Log
Kirk How old are you and what level of education do you have?
JBrett I'm 13 and in the 8th grade.
Kirk What do you plan to do after high school?
JBrett I plan to major in computer engineering...
Kirk Where do you think you want to work?
JBrett I have never really thought about it... I think I would like to work for TI designing ROM's... I think that would be cool.
Kirk What calculators do you own?
JBrett A TI-86, but I have access to all of the Z-80 calculators at my school.
Kirk Do you plan to buy any other calculators soon?
JBrett Not soon, but possibly an 89 later.
Kirk What do you use your calculator for most?
JBrett Programming =)
Kirk When and how did you find out about the "TI Community"?
JBrett I found out about it when I was in 6th grade. I got my 86 and I wanted some games and stuff for it... I first found the TI-Files, but then I found ticalc.org and I have been going there ever since...
Kirk When did you first visit ticalc.org?
JBrett Sometime in the middle of 1997.
Kirk What was the first program you ever wrote?
JBrett Hehe... a small BASIC program called "bomb". It was a menu game where you had to go around and find the bomb and defuse it... I could make it much better now...
Kirk How did you learn to program in assembly language?
JBrett Through tutorials... mostly Trent Lillehaugen's. I wish I could have had Dux's back then...
Kirk Do you have an idol TI programmer?
JBrett SCaBBy, of course =) You too, but you stopped programming =P
Kirk What projects are you working on now?
JBrett Well, a game called Combat and another called Jenga... I am also working on some secret projects right now...
Kirk You just recently joined an alliance, didn't you?
JBrett Yes, it is the ACZ... we have many exciting things in store for the 86 and 89 communities... we are already working on tutorials and such for each calculator... we are merging 86 Central with our web page, which will hopefully open shortly.
Kirk What advice would you give to people wanting to learn to program in assembly?
JBrett Start small... learn the basics first and work up... Looking at source code helps and so do tutorials.


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