The TI-nspire CAS and the Classpad 330 are the top of the line CAS calculators, and are used in both secondary and tertiary education worldwide. And each one has its passionate adherents and equally passionate detractors. However, it’s hard to find a balanced comparison (would you expect to find the TI calculator favourably reviewed in a Casio forum?) TI have released a color version: the TI-nspire CX CAS; and Casio have announced a color version of the ClassPad, to be available in the second half of this year.
For the purposes of this comparison, I’ll use the current monochrome TI-nspire CAS, and the current ClassPad 330. Here is what they look like:
Also this post will be entirely based on using the handheld calculators, not the computer software which is also available for each of them. And it will be by its very nature superficial; I hope to cover particular topics in more detail in later posts.
The TI-nspire has a screen size of 320×240 pixels; the ClassPad 160×240, exactly half the size of the TI-nspire. This means that the TI-nspire display is sharper. The TI-nspire has a menu driven system entirely driven by button presses; the ClassPad uses a touch screen controlled with a stylus. I find the TI-nspire much easier to use; I don’t particularly like jabbing the stylus at a screen with such poor resolution. It’s worth noting as a side issue that the stylus is easily lost; they seem to get looser in their housing with age. And many second hand ClassPads are advertised with “stylus missing”.
The ClassPad also defaults on readability. Here’s a couple of screenshots from Casio:
Note that at the top of the screen there is a menu bar, underneath of which is a “toolbar”. At the low resolution of the screen, I find the toolbar icons to be all but unreadable. Some of them are menu headers, which when selected produce a tools menu. This is a list of tiny icons, which to my eyes could mean anything. (Even with my reading glasses, and my eyesight, though not as sharp as once it was, is not that bad.) It may have been a cost issue: producing a touch screen cheaply, but I find the low resolution of the ClassPad a real hindrance to its use.
Commands on the TI-nspire are usually obtained with at most 4 keystrokes: a menu key, then at most 3 menu choices. Commands on the ClassPad, resolution notwithstanding, are also fairly easy to obtain, either with the menu bar, or from the onscreen keyboard. This image:
shows that Casio have in fact designed a very clever interface which makes good use of the limited space to obtain most commands and functions easily.
For comparison, here is a TI screenshot, showing a linear function and some values:
Note that the screen, though maybe cluttered for some, is still quite readable and sharp.
The TI-nspire uses a “Documents” system, and a document may have any number of different “pages”: calculation, geometry, lists & spreadsheet, data & statistics and so on. Variables may be transferred between pages, so that a variable, say a list created and named in a spreadsheet, can be opened in a calculator page. The ClassPad has “eActivities”; here is a description from a Casio page:
An eActivity is a new, exciting innovation. It is small packet of learning that can be written by anyone, even yourself! It is loaded into the calculator and a student is then free to work through it. It is normally a scripted learning experience that has all the functions of the calculator at its disposal. eActivities can be used to present students with assignments, learning opportunities or in fact to build your own simple software…
I think that the calculators are much of a muchness here. True, the ClassPad offers some goodies such as the Laplace and Fourier transforms, which might give it a slight edge. However, there are also a few anomalies. The TI-nspire provides LU factorization of a matrix in the form of the matrices , where is a permutation matrix for which ; the ClassPad just returns and . This means that given a matrix the ClassPad will return and matrices for which possibly . An example is the matrix
This may be a small worry, but surely it’s a simple thing and worth getting right?
I haven’t applied (as yet) a CAS test-suite to either calculator. You have to remember that in terms of raw computing power, these calculators are lightweights, and can only be expected to solve relatively small problems. But here’s one test I did yesterday. On the TI-nspire, I found the factorization of Cole’s number:
performed almost immediately. Impressive! Just to check this wasn’t a fluke, I obtained the following factorization:
in a little under three minutes. I tried the first factorization on the ClassPad and got nothing in a reasonable time (several minutes). So either the TI-nspire uses a better factorizing algorithm, or it has a more powerful processor.
This is an issue I’ll try exploring in more detail in later posts.
Variables and programming
The TI-nspire has three ways of assigning a value to a variable:
- Define x=3
- 3 x (the arrow is obtained by using the “sto” key)
- x:=3 (The “:=” is obtained with two key presses: crtl, :=)
The ClassPad has two ways:
- 3 x
without, however, any single key to obtain “:=”. And only the arrow method can be used in programs.
Both calculators use a version of Basic on the handhelds. Apparently the scripting language lua can be used with both, but I suspect only on the associated computer software, and not directly on the handhelds. And they both provide the full gamut of control statements (loops, tests etc). Both calculators distinguish between functions and programs, although in slightly different ways.
The ClassPad offers very nice sequence handling: you can set up a number of interlinked sequences, and set ‘em off. For example, you can enter
(which are the sort of equations which may be encountered in Jacobi’s iteration method for linear equations), in the Sequence page, and just run them. The TI-nspire has a “Lists & Spreadsheet” page, in which you can perform similar calculations, but not as elegantly as this.
As a mini-comparison, here are for-loops on each:
|For 1i to 10
Both calculators support 2D graphing (they would hardly have a market if they didn’t). The ClassPad also supports 3D graphing, which is supposed to be a huge feather in its cap, but in fact I find this to be of limited use. Just as an experiment, I attempted to plot the monkey saddle surface and couldn’t make any sense of the result. Even with zooming, moving the graph around with the stylus, I couldn’t obtain any intuitive feel of the shape of the graph. Partly this is because there doesn’t seem to be any hidden line algorithm available. However, the drag and drop capability of the ClassPad, with the stylus, is one area which it shines. The TI-nspire’s touchpad, although it works, is clumsy in comparison.
Which is better?
I much prefer (for my purposes) the TI-nspire’s sharper screen and interface. However, when the new colour model fx-CP400 is released I will certainly reconsider. I have no loyalty to either brand. In the end, it comes down to what you and everybody else is using. My daughter is using a ClassPad 330 for her year 11 mathematics (its use is mandated by her school) and is very satisfied with it. I would imagine that even with the models discussed in this post (the monochrome TI-nspire already superseded, the ClassPad 330 about to be), either one would happily manage pretty much all school, and most college, mathematics.