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Retro Review: TI-68
07-23-2017, 03:32 PM
Post: #1
Retro Review: TI-68
Excerpt:

Years: 1989 - 2002
Type: Scientific, Formula Programming
Memory: 440 bytes, in 55 8-bit registers
Operating System: Algebraic
Memory Registers: Up to three characters

Batteries: 1 CR2032

Link: http://edspi31415.blogspot.com/2017/07/r...ti-68.html

[Image: 2017-07-23%2BTI%2B68.jpg]

What I love about the TI-68 is how complex numbers are integrated in the operating system. There is no need to switch to a separate mode. Best of all, the TI-68 handles exponential, logarithmic, power, and trigonometric functions with complex numbers.

The simultaneous solver also allows for complex numbers. This is indeed rare, as not even most graphing calculators’ simultaneous solving apps allow for complex numbers as coefficients. (Note: The HP Prime’s simult command allows for complex numbers)

Complex numbers on the TI-68 are notated as such:

Rectangular: (x, y)
Polar: (r ∠ θ)

Part extraction of complex numbers works slightly different: real and imag extract the real and imaginary portions of the complex number, regardless of setting.

Choosing the Precision?

The TI-68 allows for two precision settings: 10 digits or 13 digits. The display uses 10 digits. I think this is a rarity, if not a completely unique feature, since calculators in general uses an accuracy of 13 to 15 digits automatically.

I tested a couple of integrals and the precision setting does not affect the length of time either way. Both integrals were calculated in about 3 seconds.

Test Integral 1: ∫ (T^3 * e^(-T) dT, 0, 100, intervals = 6)
Test Integral 2: ∫ (X^2/(X^2 + X – 1) dX, 25, 75, intervals = 12)
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05-25-2021, 02:18 PM
Post: #2
RE: Retro Review: TI-68
Yes, I don't know who in their right mind at TI thought it was a good idea for the 'real' and 'imag' functions to operate like that! Almost as bad as the TI-84's exponential format showing angles in degrees.

— Ian Abbott
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08-08-2021, 03:11 PM (This post was last modified: 08-09-2021 02:26 AM by jhallen.)
Post: #3
RE: Retro Review: TI-68
I remember these, thought they were pretty good looking calculators when they came out. I think the Radio Shack version of it looks even better.

But I find the user interface to be somewhat inefficient- I wondered if they were trying to avoid looking too much like Casio fx-4000p:

There is no backspace, only delete (and it's shifted).

When you hit Shift-ANS, it puts the actual number in the edit buffer, not symbolic "ANS". RCL does the same thing. You could make arguments either way for this.

You have to hit Alpha after RCL, even though the variable must be a letter.. why doesn't it auto-Alpha?

You can "replay" the previous equation, but it's weird (as a Casio user) that you have to hit Shift-EQN to get it back instead of left arrow.. but whatever.

I like the formula memory, though there are too many prompts when using it. Like do you really want to calculate this formula YN?

Oh one more thing: is this possibly the first calculator with a hard slide-on cover? Maybe first scientific calculator like this..
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08-09-2021, 04:42 AM
Post: #4
RE: Retro Review: TI-68
(08-08-2021 03:11 PM)jhallen Wrote:  Oh one more thing: is this possibly the first calculator with a hard slide-on cover? Maybe first scientific calculator like this..

I think that's a really interesting question.

I can't speak with authority but I believe the TI-30 SLR+ predates the TI-68. It has a slide-on cover. I'm betting there are even earlier examples. I thought maybe the fx-7700g but that came out after the TI-68.

The TI-68 is one of my favorite calculators in terms of form and function. It was no longer in vogue by the time I was old enough to have need of a scientific. As Eddie alludes to, the displays seem to be delicate and of the three examples I've laid hands on, all three had issues. I was able to restore one of them to full function using a heat gun on the LCD ribbon connector. It's anyone's guess how long that repair will last.
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