Thank you for reading the ticalc.org newsletter! Today is the start of a new year, and we here at ticalc.org have many exciting surprises in store for the coming year. The promised changes to this newsletter, unfortunately, have not yet been effected. Please ignore the small problem with Dux's name; my newsletter generator was not set up to handle names shorter than mine!

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 choose in the "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.

The Program of the Month award will begin with the month of January. At the end of January, Bryan Rabeler and I will select some programs from each of the following categories: 82asm, 83asm, 85asm, 86asm, 89/92+asm, 92asm, and TI-BASIC. The newsletter will give voting instructions and give a brief description of each choice. Then, for a week, registered voters will be able to vote for the program in each category they like the best. After the results are in, an addendum to the newsletter will be released reporting the winners. At the end of the year, all of the Program of the Month winners will be rounded up and there will be a grand survey to determine the Program of the Year in each category.

Kirk Meyer

Not an error, just an observation regarding your feature on the SIMULT mode of the 85/86:

Any TI that I know of with matrix capability (82, 83, 85, 86, 89, 92, 92+, and maybe even the 80 & 81) can solve simultaneous equations, and often (if you're fast on the keys) faster, without needing to jump out of a program or the Home screen. Assume you have equations a*x+b*y=c and d*x+e*y=f. Create matrix G (for example) containing [[a,b,c][d,e,f]]. To solve the equations, use the RREF command on G. For the TI85 and TI86 use rref G, and for the 89/92/92+ use rref(g). You will get a matrix which looks like this: [[1,0,x][0,1,y]]. The pattern holds.

If for some reason you have matrices but not RREF, create matrix G as usual but create matrix H as well, which looks like [[a,b][d,e]]. Execute the command F^-1*G. You will get the same result: an identity matrix of the same dimension as the order of the system with the values of the unknowns in the tacked-on far right column. Besides, using RREF is faster than that hated simult() on the 92/92Plus. Thank you, TI, for giving us the Reduced Row Echelon Form (which also works on HPs, but you don't care about that, eh? ;)

Chris VanderKnyff

Quite a lot happened in calculator news this past month. Brandon Sterner, a member of the TI Calculator Programming Alliance, has released Yoshi v1.0 for the TI-83 (SOS). Yoshi, in some ways, is similar to Tetris. Additionally, Sam Heald has released Baseball '99 v1.0. Thus far he has released versions for the TI-82 and the TI-83. There are real modes of play, real baseball teams and rules, fast gameplay, and good graphics. Source code may be released later.

In TI-89/92+ news, The Doors Team has released the Doors OS v0.96 Beta as well as the Doors GUI v1.81. New features include improved Anti-Crash protection, improved Shift-ON Combo, new font table addresses in DoorsOS.h, new handles.txt in the docs, new function getfreearchive in userlib, and more! The Doors Team says this should be the last beta version, as it is supposed to be "really stable now". These files are available at ticalc.org.

Turning our attention to calculator sites, some interesting things have happened. We, ticalc.org, have broken our previous record and had mroe than 40 million requests on December 21st. Dimension TI has begun to sell calculators and link cables from their web site. Dimension TI has some of the lowest prices available for purchasing TI graphing calculators.

In response to the release of System Monitor, a program which measures the level of the batteries in a TI-86, I have received a great number of requests to create a clock for the 86. I cannot be sure about the 73, 89, 92, or 92+, but I do know that it is not possible to create a clock for Z80 calculators. Although that would be neat, there are a couple of reasons why this is not feasible.

While it is on, your Z80 calculator generates an "interrupt" about every 1/200th of a second. This interrupt controls things such as cursor blink, the busy indicator, etc. If you push ON, however, an interrupt is generated that is not one of the timed interrupts. "So what," you may ask. Well, in order to turn the calculator off you must also turn the timed interrupts off. This way nothing happens like cursors blinking until ON is pressed. Once ON is pressed, timed interrupts are returned to their normal state.

This means that a clock is not possible on a Z80 calculator, because timer interrupts do not occur while the calculator is off. The calculator would only be able to keep track of the time while it was on. Furthermore, the frequency of the timed interrupts varies with battery level which would make the clock run more slowly as you used the calculator more. Although it is a nice idea (and I'd like it too), a clock on the Z80 calculators is simply not practical.

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