Texas Instruments TI-55-II

Date of introduction:  1981 Display technology:  LCD
New price:  $50.00 (SRP 1981) Display size:  8 + 2
Size:  5.8" x 3.1" x 0.90"
 147 x 79 x 23 mm3
Weight:  3.7 ounces, 106 grams Serial No:  210035
Batteries:  2*LR44 Date of manufacture:  wk 37 year 1981
AC-Adapter:   Origin of manufacture:  USA
Precision:  11 Integrated circuits:  TP0455/CD4505, CD4506 or TP0456/CD4555, CD4556
Memories:  1-8    
Program steps:  56-0 Courtesy of:  Joerg Woerner
Download leaflet:   (US: 2.2M Bytes) Download manual:   (US-QR: 1.5M Bytes)

With the TI-55-II Texas Instruments added in 1981 a new calculator line to the existing slimline series. In you compare the slanted TI-55-II with a typical slimline calculator like the TI-53, you will notice some changes:

Larger display gives 8+2 digits instead 5+2
45 keys instead of 40 keys
More space for the electronics

TI-55-II_LTA2984_KBD.jpg (194675 Byte)TI-55-II_MOLD.jpg (371587 Byte)The display was not in one line with the keys but slanted towards the user. Together with a perfect contrast and large digits the calculator looked very professional. In practice the keyboard of all members of the slanted scientific/financial calculators was terrible, either bouncing or without any contact. Most users of the TI-55-II remember: "The -II designation was evidently for the number of keystrokes that were recorded with one button press". The calculators were usually replaced for free by Texas Instruments with TI-55 III's which did not inherit the bad genes of their forefathers.

Some very early calculators of the second generation were sold under the old designation TI-55 II with just a missing hyphen.
View a very rare TI-55 II manufactured in Taiwan here.

TI-55-II_IC.jpg (289543 Byte)The two-chip design of most slanted calculators allowed more features compared to the slimline series. The TI-55-II for example added a total of 8 memories to the basic functions. Find more information about the TP0456 calculator chips here. The TI-88 added a third microcontroller to this Master/Slave approach.

Known from the TI-53 and the original TI-55 is the simple programmability, here each memory could be converted to 7 program steps. A nice enhancement was a function to integrate with the Simpson-rule. If you are interested in the calculating accuracy of scientific calculators, don't miss the Calculator forensics.

One calculator in the TI-55-II series - the TI-54 - could manage arithmetic with complex numbers. Once again a "first" from Texas Instruments.

Don't miss an early prototype of the TI-55-II and the famous TI-88

In Brazil the housing of the TI-55-II was changed to accommodate two AA-sized batteries instead the small coin shaped LR44 type. View this rare beauty here.

The US based company Jeppesen Sanderson developed a very interesting navigation computer called prostar based on the TI-55-II.

The TI-55-II is featured in the Texas Instruments Incorporated bulletin CL-580 dated 1981.

Find here an excerpt from the Texas Instruments Incorporated leaflet CL-199J dated 1981:


Advanced LCD slide rule calculations with programming and statistics.

With 112 powerful functions for professional engineering, science, and math applications. Easy keyboard programmability; including function evaluation and integration features, saves time on repetitive problems. Also the most needed statistical functions for better data analysis. Use up to 8 memories. Built-in conversion functions for fast transition between various measurement systems. Plus: roots, powers, reciprocals, log, trig and hyperbolic functions. Enter data in standard, scientific, or engineering formats.
Comes with the revised and expanded edition of Calculator Decision-Making Sourcebook that shows how to use all its power.

Texas Instruments, 1981

The TI-55-II is featured in the Texas Instruments Incorporated leaflet CL-199M dated 1983.


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If you have additions to the above article please email:

Joerg Woerner, December 5, 2001. No reprints without written permission.