HP-11C scientific calculator

The calculator.

Brand name Hewlett Packard
Model number HP-11C

- Picture of HP-11C keyboard [link opens in new window]. (Provided by the author of this page.)
- My HP-11C FAQ.
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Logic system. Does your calculator use algebraic or RPN (reverse Polish notation) logic? How do you tell? An algebraic calculator has an = key; An RPN calculator has an ENTER key. To add two numbers (say, 2 & 3) on an algebraic calculator, you type the keys "2 + 3 =". On an RPN calculator, you type "2 ENTER 3 +".
Algebraic or RPN? RPN. This calculator has an ENTER key (big key, middle of bottom row), and does not have an = key.
Algebraic calculators can be further subdivided into AOS and DAL. If you know which type yours is, you can write that here. Otherwise, you will figure that out later on the form. n/a for an RPN calculator

Shift keys. Shift keys are used to get the second (or third) function for a particular key. If there are two shift keys, list both.
What is the label on the "shift" key(s) yellow shift: f
blue shift: g
Where is the shift key? Both are near lower left.

Scientific notation; entering. Identify the key used to enter the exponent. (It is usually EE or EXP, or similar.)
* A special case concerns entering a number that starts with 1x in scientific notation: do you need to enter the 1? Try it... Calculate 1x1012 * 2. Do it twice, once with the first 1 and once without it. Do you need to enter the 1 to get the correct answer, 2x1012?
* The key for making an exponent negative is the same key used for entering negative numbers.

What is the label on the key for entering exponents? EEX
Where is that key? middle; just above "ENTER"
When entering a number that starts with 1x in scientific notation, do you need to enter the 1? (e.g., 1x1012) no; ok to enter just EEX 12
What is the key for making an exponent negative? CHS
Where is that key? Top row, middle, above EEX.

Scientific notation; display.

Most scientific calculators allow you to "force" the display to use (or to not use) scientific notation.

Many calculators allow you to set the number of decimal places displayed.

(Some calculators also have an option for "Engineering notation", which is a variation of Scientific notation. Not important for most people.)
The SCI key (f-shift 8) sets the display to scientific notation.
The FIX key (f-shift 7) sets the display to fixed decimal notation.

You must follow the SCI or FIX key with a single digit (0-9) specifying the number of decimal places.

f-shift SCI 4 -- sets the display to scientific notation with four decimal places.
f-shift FIX 0 -- sets the display to fixed decimal notation with zero decimal places.

Logarithms (and anti-logs). In intro chem we most often use base 10 logs (log10), for example with pH. The log10 is the power of 10 of the number. For example, the log10 of 1000 is 3; and then the antilog10 of 3 is 1000.
* On some calculators, you press the LOG key before the number, and on some you press the number then the LOG key.

How is the log10 key labeled? LOG (in blue).
It is g-shift 10x.
How is the base 10 antilog key labeled? 10x
To take the log10 of 1000 which do you enter first, the number or the LOG key? The number. That is, enter 1000 g-shift 10x.
That holds for other one-key functions, such as antilog and square root: enter the number first, then the function.

Base e logs (loge or ln) are called natural logs. We do not use these in intro chem, but you are likely to use them if you go much beyond that.
How are the keys labeled for natural logs and antilogs? LN (in blue).
It is g-shift ex.

anti-log: ex

Miscellaneous. These are functions we do not use in intro chem, but which you are likely to use in other math and science courses. Briefly noted here.

Angles: degrees or radians

(Some calculators also have an option for "grad". The grad is 0.9 degree, so that a right angle is 100 grad. Not commonly used.)
DEG (g-shift 7) sets the calculator to work in degrees;
RAD (g-shift 8) sets it to work in radians. (In radians mode, RAD appears on the display.)

There are also keys to convert an individual entry from one form to another. These are -->RAD (f-shift 3) and -->DEG (g-shift 3).
Polar vs rectangular coordinates -->R (f-shift EEX)
-->P (g-shift EEX)
Both of these functions work on a pair of values, in the X and Y registers.

You. Please provide your name and e-mail, so I can check back with you if there are questions (and maybe have you proofread the web page for your calculator). We will not list your name at the web site without your explicit permission. We will not make your e-mail available in any case.

May we list your name in the collection (at the web site), to give you credit for providing this information?
If yes, how would you like your name listed? ("handles" ok.)
Bob Bruner

   (Or perhaps it is a FPP = frequently posed problems.)

I'm happy to accept contributions -- or corrections.

Problem: Decimal points appear as commas, and vice versa.
   - Turn calculator OFF.
   - Hold down the . (decimal point) key, and turn calculator ON while holding down the . key.
   - Release the . key.

Explanation. In normal American usage, we use the "decimal point" (a period) as the "radix mark" -- to separate the integer and decimal parts of a number. We also use commas to separate groups of three digits. In some places, the dot and comma are used exactly the opposite way. The HP-11C allows either convention. Of course, normally one wants one of them -- permanently -- so the switch is not very convenient. In the manual, look up "radix".

Problem: The word "USER" appears on the display (under the regular numbers).
Solution: f-shift USER (which is on the RCL key) will toggle USER on and off.

Explanation. In USER mode, the primary and f-shifted meanings of five keys (top row, left, from square root to 1/x) are reversed. This can be useful if you are running programs where you need to make much use of the A-E keys, to designate program segments. For all ordinary use of the calculator, you do not want to be in USER mode. Being in USER mode interferes with normal use of those five keys (though you can access the original primary functions by prefixing them with f-shift). In the manual, look up "USER annunciator" or "User mode".

Problem: The word "GRAD" or "RAD" appears on the display (under the regular numbers).
Solution: g-shift DEG (which is on the 7 key) will turn those words off. (If you use trig functions, I suggest you read the explanation below, and decide if that is what you really want.)

Explanation. This deals with trigonometric functions and how angles are measured. The calculator can use three different units for measuring angles: degrees (DEG), radians (RAD), grads (GRAD). To choose a trig mode, you use the g-shift followed by 7, 8 or 9 respectively (see the blue labels on those keys). If you are in RAD or GRAD modes, those words appear on the display; if you are in DEG mode, which is the default, no such word appears.

These modes only affect trig functions; if you do not use trig functions, this setting will have no effect. If you do use trig functions, you need to decide which angle measurement you want. My main suggestion above, to set it to DEG, is based on the assumption that if someone asks, it is likely they had not previously noticed any word there.

There is a little more information about angle measurements above, under Miscellaneous.

In the manual, look up "Trigonometric mode"; the 2nd of three page numbers is the main one of interest.

Problem: A flashing asterisk * appears on the display (lower left).
Solution: Replace the batteries. Soon.

Explanation. The flashing asterisk * is the Low Power Indication. Information on battery model and replacement procedure is in the manual. If you don't have that... Eveready A 76 (alkaline) or 357 (silver oxide). Stores that sell batteries are usually good at knowing the equivalents for other brands. They are also good at identifying the battery if you just show them one. (If you do that... Make sure calculator is OFF; take out the battery at the time you need to, and put it back in immediately. If the batteries are out for more than a brief time, stored memory contents will be lost; the calculator is not damaged, however.) In the manual, look up "Low power indication" or "Batteries".

Problem: Calculator is unresponsive to keystrokes. The word "BEGIN" appears on the display (below the numbers).
Solution: Not sure. This should not happen, and seems to reflect some kind of electrical malfunction. The problem is discussed, in a users' forum, at: https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv006.cgi?read=11149. One user told me privately: "I removed the batteries and left the calculator overnight. Lo and behold when I refitted the batteries the calculator works fine." His previous efforts to resolve the problem by removing the batteries "briefly" had failed.

DISCLAIMER. Neither I nor any person or organization referred to here can take responsibility for possible damage to your calculator if you follow any of the suggestions. As noted, this symptom seems to reflect some electrical malfunction. It is possible that the details will differ in different cases. It is also possible that in some cases the situation is terminal. Remember, if your calculator has this problem, it is not functional. If you are able to get it working again, that is a bonus, but perhaps you will not be able to. Proceed at your own risk.

Problem: A manual?
Solution: The Museum of HP Calculators: https://www.hpmuseum.org/. Among their resources is an extensive collection of manuals, which they sell at a modest cost.

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Last update: November 27, 2021