HP-16C versus SR-22


Hello to all lucky owners of a HP-16C.
Recently I received an oldfashioned Texas Instruments SR-22 and noticed that this rare beauty performs a conversion between a decimal floating point number to OCT, HEX and vice versa. Example:

1.23456789E12 converts to

2.175617660 E17 Base-8 or

1.1F71FB044 E0A Base-16

Highest decimal input is

9.999999999 E99 converts to

1.249AD258D E53

My question: Is the HP-16C - or any other known calculator - able to perform similar (stupid?) calculations ?

A picture is here: http://www.datamath.org/Desktop/sr-22.htm

Greetings from Germany,

BTW: Merry Christmas and Happy New Year plus Great calculator hunting plus all my best wishes that HP returns with a RPN calculator and stops selling rebadged Citizen stuff...


Hello, Joerg;

The HP16C works only with integers when in one of the four basis, i.e., both decimal point/radix mark key [.] ad enter exponent [EEX] are even disabled, they work only in floating point calcualtions. And in this mode, the HP16C works only with decimal numbers.

BTW, I'd send you an e-mail about it: I have a friend who own a PC200 and does not have a calculator to use with it. So, I am telling you that BA55 is travalling to another country, O.K.?

Good reading your posts here.

Best regards.


The HP 16C does perform conversions between floating point and the integer modes (and vice versa), though not in the most obvious way.

When converting from integer to float, it takes the values in the X and Y registers and converts them into y * 2 ^ x, with the result being left in the FP X register. Switching from float to integer does the reverse calculation.

This is not what most people expect, especially these days. However, the 16C manual does provide a couple of programs for converting between the 16C's floating point decimal format and IEEE 754 single-precision (32-bit) floating point.


--- Les



you're right. There is an IEEE standard for representing binary numbers (not integers) in a 32-bit word like this:

 s      e             f         (IEEE proposed format)
31 30 23 22 0 (bit #)

where s is the 1-bit signal, e is the 8-bit biased exponent and f is the 23-bit fraction.

As the HP16C representes floating point numbers in a ASCII fashion, the equivalence beteween the floating point numbers and the binary integers in the HP16 is accomplished with [FLOAT] n and any of the four base keys: [BIN], [OCT], [DEC] and [HEX]. When toggling from floating point to any of the integer bases, one binary integer is obtained from the values in Y and X registers, like this:

(integer in selected base) = Y . 2^X

This equivalence is preserved when toggling back.

The Programs for Format Conversion provided in the HP16C manual demonstrate how to convert from internal HP16C's floating point decimal and IEEE floating point binary (single precision) and back.

None of these operations are equivalent to the ones shown in the SR22, and I believe this is mostly because this calculator seems to allow binary numbers to be entered, not supported by the HP16C that only accepts single binary integers as input data.

Am I correct or I missed something?



The HP-16C is a calculator.

The SR-22 is an airplane.

Sorry, couldn't resist.


Sure - a neat one. But as calculator it outdates the HP-16C about 10 years - and the HP perform worse in some kind of your everydays usage:

SR-22 vs. HP-16C

Keyboard: Real keys against Chicklet knobs

Display: Strong red LED readable without glasses at night

Base-16 conversions: Floating vs. Fixpoint

Battery usage: None vs. little bombs

So long, keep your humor ;-))

Merry Christmas and Happy New Year !


Not a calculator, but Derive on my HP200LX can do essential stuff like pi to 1000 decimal places in binary (or any number base up to 36)

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