Texas Instruments BA II Plus Calculator for iPhone

Along with the Hewlett Packard HP-12c, The Texas Instruments BA II Plus financial calculator has been a steadfast companion for business students, real estate agents, and money managers for years. On September 14, TI released the iPhone (and iPod touch) app, identical to the physical calculator. While the implementation is superb, small details detract slightly from the product.

This calculator has a myriad of financial, statistical and a few scientific functions. One has to actually read the User Guide to fully exploit the calculator's various financial functions. I'll trust that TI implemented those without error in this quick look review. Instead, I'll focus on some of the nuances.


Settings. Unlike many calculators, the settings aren't accessed with a special key or badge on the face. Rather, one has to go to the iPhone's settings page and scroll down to BA II Plus. The only setting there is the key clicker.

Key Clicker. The clicker sound is long, harsh, and sounds old fashioned. It also seems to slow down keyboard input. A crisper, more modern sound would be welcome.

Input Logic. One of the reasons people use RPN calculators is to avoid input and calculation errors. A tradition with TI is the choice between Chn and AOS input logic. In Chn, an expression is evaluated left to right. Period. In AOS logic, the mathematical hierarchy of operations is respected. For example, exponentiation first, then mult/div and finally plus or minus. The default in this calculator is Chn, and that's a shame because if you enter, for example,

2 + 3 x 4

You'll get an answer of 20 which is wrong by normal convention. The right answer is 14. If you're accustomed to this on the physical calculator, there won't be a problem. However, new users to the calculator are urged to switch to the AOS input mode.

Being somewhat new to the calculator, I searched in vain for the "EE" key to input an exponent. Also, in what seems to be a TI tradition, the way to do this is with the y^x key. Be aware of that. So to enter 1E21, you enter 10, y^x, 21 and then another operator. The display, if you just hit the "=" key will display "1. 21". That isn't a very modern approach to exploiting the graphics capability of the iPhone -- where one would expect to see typeset-like exponents -- as in PCalc or CalcZero.

iPhone Technology. Along those lines, there isn't much in the way of using modern iPhone capabilities. There's no "Shake to clear." There's no use of the swipe, like PCalc, to modify settings. There are no key popup labels as with CalcZero. That's a bit disappointing. The implementation on the iPhone should be an opportunity to move calculator state-of-the-art forward, not just mimic the limitations of the past.

Manual. Unlike the HP-12c and 15c for the iPhone, there is no imbedded manual. The User Guide and Quick Reference Card, however, are free, and the PDF can be downloaded from TI's Calculator site.

Because the settings are limited, there's no way to change the look of the display. However, I'll give the developer big time props for selecting black numbers on a pale green display. It looks good to the eye -- even if the display is hardwired to the seven segment numerals of the past. This was, in the words of Emerson, a foolish consistency.


I think that users of the BA II Plus in its physical form in the past will be delighted. The iPhone implementation is faithful, and the free manual is thorough. However, I would recommend that the calculator be used by people very familiar with TI calculators, their input logic techniques, and the financial calculations supported. It's a complex and capable financial calculator, not a casual one designed to be used by someone who just wants to compute a 15 percent tip at lunch.

The TI BA II Plus requires iPhone OS 2.1 or later and is priced at $14.99.