Monday, February 19, 2018

Retro Review: Texas Instruments BA-55

General Information

Company:  Texas Instruments
Type:  Programmable Finance
Memory:  40 steps, 10 cash flows
Battery:  2 * A376, LR44, or SR44
Years:  1982 - 1986
Editions:  2:  1982 (BA-55), 1986 (BA-54)
Original Cost: Unknown


There are four main categories of functions that are provided with the BA-55:  programming, time value of money (finance), cash flows, and statistics including linear regression, separated into three modes.  The programming and finance categories are combined in a single category.  Switch modes by pressing [ 2nd ] [ R/S ]. 

Program/Finance Mode

Time Value of Money:  The BA-55 has the standard time value of money solver, with the interest key, [ %i ], working with periodic interest.  In annuities, you can calculate principal and interest for a single payment, accumulated interest, and balance.  The keystrokes are:

Principal/Interest for a single payment:  [ 2nd ] [ N ]

Accumulated interest from payment 1 to n: [ 2nd ] [ i% ]

Balance after n payments:  [ 2nd ] [ PMT ]

There are also two keys for interest conversions between nominal ( [APR>] ) and effective ( [<EFF] ) interest rates are available.

Programming:  The programming module of the BA-55 is basic, with a maximum of 40 steps.  The number of memory registers, which top out at six (R0 – R6) decrease with every eight steps, and the memory will be allocated automatically.  One of the best features is that during programming, the screen will show how many memory registers are available.   Memory register 0 will always be available. 

The reset instruction ( [ RST ] ) points the instruction point to Step 00 and will continue.  This allows for simple loops. 

The BA-55 operates on a chain operating system, not the algebraic system.  For example, pressing 2 [ + ] 3 [ * ] 4 [ = ] returns 20.  So be careful. 

Cash Flow Mode

The BA-55 can handle up to 11 cash flows, which I implied from storing the initial cash flow in PV, the other cash flows stored in registers 1-9, with the last one using the sequence [ STO ] [ . ].

Net Present Value:  [ 2nd ] [ PV ]

Initial Rate of Return:  [ 2nd ] [ FV ]

The interest rate is stored with the [ %i ] key.

There is only one memory register available in this mode, register 0.

Statistics Mode (Linear Regression)

The BA-55 handles one and two variable statistics.  Since this is an older calculator, entering data will cause the BA-55 to process of a half a second before showing you the data count.  You can calculate the slope, intercept, and correlation using the linear regression model, and it is nice that the keys are labeled descriptively with Slope, Intcp, and Corr, respectively.

However, the statistics features on the BA-55 are stripped.  Missing are the forecasting function for x (there is a forecasting function for y), the data count (n), and the sums (Σx, Σy, Σx^2, Σy^2, Σxy).  Given that there are only a maximum of four registers (R0 – R3), I was mistaken to think the sums would be allocated to R4 – R9. They are not.

Like in the Financial/Programming mode, memory register 0 will always be available.

What Was Up with the Colors on the Keys?

One of the most peculiar things about the BA-55 are the colors used.  On the 2nd row from top, I could see the primary markings OK (black on tan), but the secondary markings are light, faint gold against a taupe background.  The secondary text is so light you wouldn’t even notice that they were there.  If you purchase a BA-55, make sure you get the manual (or the manual of a BA-54).  For the record the second row of keys are:

[ N ]  (2nd:  P/I)
[ i% ] (2nd: Acc)
[ PMT ]  (2nd:  Bal)
[ PV ] (2nd: NPV)
[ FV ] (2nd: IRR)

On the first row:

[ CPT ] (2nd: Due)

On the fourth row from top, the secondary markings are in pink, and the text can clearly be seen.  I wish TI applied this color scheme everywhere where the keys that were on a taupe background.

Thankfully the color scheme for the BA-54, the successor to the BA-55 (no, that’s not a typo), improves on the color scheme.  You can check the two pages from  for more details. 

Printer Features

A unique feature to the BA-55 are the four printing functions Adv (advance), List (list the program), Print, and Trace.  This allowed the BA-55 to be connected to a PC-200 printer.  The PC-200 printer was also made for the TI-66.


I like the design of the BA-55 with its tilted display.  The keys are easy to press and are responsive.  Again, there is a slight processing time due it being an older machine.  The colors of the BA-55 though, could use improvement.

As I mentioned before, I think the programming module is more a secondary feature than a primary one.  Unfortunately, the only mode the program steps are allowed is the Financial mode. It is nice for it be available for quick calculations but it wouldn’t beat the HP 12C’s programming module.  I would have liked to see the programming available in all the modes.

And there is no days between dates function either.  (That particular function doesn’t show up on TI’s basic financial calculators, so that is to be expected.)

As far as a basic financial calculator, the BA-55 will do the job.  The programming, while limited, provides for some storage of a quick calculation.  I also like the pouch and the well-written quick reference guide.


This blog is property of Edward Shore, 2018.

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