Frequently Asked Questions

A calculator is more convenient than anything else when in the field and provides a tactile keyboard which gives positive feedback, ensuring your input is complete.

The C47 has a better screen than any classical HP calculator, a faster and more powerful processor, more memory, long battery life and allows very precise calculations and the support of advanced functions, matrix operations and complex numbers surpasses anything else on the market. The support of fully customisable number display options is totally unique. The C47 also supports many conversion functions.

The C47 can be considered as a superset of the features of the HP-15, 16, 41 and 42, but it is not binary compatible with any of those.

On the Wiki, a build instruction is specified for all three platforms here.

Every function and command and setting is documented in a set of reference documents available as many pdfs on the website. This also includes a growing set of application notes. A limited tutorial style description is available on the Wiki.

34 digits for real numbers are visible to the user for display and storage. Internally it uses 39 digits for real numbers to allow for rounding. Additionally an integer type is available for arithmetic, display and storage of up to 1000 digits for integers.

The calculator is built for real‑world tasks that demand precise results. It combines the GNU Multiple Precision Arithmetic Library (GMP)—an open‑source library for arbitrary‑precision signed integers, rational numbers, and decimal floating‑point arithmetic—with the decNumber library to provide correctly rounded, IEEE 754‑2008–compliant decimal arithmetic.

Yes, quite effectively since all planned math and programming is working.

The use of RPN is learned in a few hours maybe and the calculator is based on a strictly logical input scheme, where functions take arguments from the stack and commands can use trailing input, with simple prompts. Functions and commands are located on the keyboard and/or in menus accessible from the keyboard or from other menus, or catalogs. Temporary Information items describe many types of output (calculation results).

Read this article on The Museum of HP Calculators.

RPN has been the de facto Engineering standard of the 70s and 80s, for a good reason. C47 continues that tradition.

RPN allows making calculations in real world problems, as opposed to educational problems which often have formulas given. Real world problems require chaining results of one calculation into the next, which is the normal way a RPN calculator operates, using a stack.

Over time, the notion emerged that values being keyed in belong in an input buffer separate from the stack, and only copied to the stack when entry was finished, either by pressing ENTER or a function or operator which then "closes" the entry "mode".

This behaviour has been called Entry RPN or eRPN for short, and is different from classical RPN where the transition of values onto the stack follows some slightly more elaborate rules. See HP RPN Evolves for more details.

The difference in behaviour produce different results:

• Entry RPN: 47 ENTER × results in 0
• Classical RPN: 47 ENTER × results in 2209

eRPN/RPN is selectable in the C47 MODE menu.

eRPN takes advantage of the input buffer where values are entered before they are put on the stack using ENTER (the classic RPN calculators did not have a separate input buffer). This means that a value is not duplicated on the stack, which is a more efficient use of the 4 or 8 stack registers.

The C47 does not use RPL, nor will it ever.

The C47 uses RPN for all interactive and programmed operations but can use algebraic formulas for plotting and solving.

Yes. And No. Functions visible on the keyboard are generally intuitively usable for pre-calculus students. However, the same visible functions can be used in advanced ways in the complex domain where university and high school backgrounds will help. Many more functions in menus and sub-menus will need understanding of number theory and calculus.

Many fields of professional expertise are supported by the calculator, most notably, engineering, with some special EE menus, advanced mathematics, matrixes, vectors, statistics, probability distributions, finance, number bases, binary operations, computer science, etc.

The firmware is in beta for the foreseeable time but it can be used for real work already.

It is an open source project by unpaid volunteers. The answer is always, if a specific feature bothers you, you are welcome to code it and send a merge request on GitLab.

• IR printer support
• Serial support (unlikely to be supported on the hardware platform)
• 1 or 2 string functions
• 3D vector polar/rect support
• Matrix concatenation
• And maybe a few items more...

Prototyping phase has started. Announcement on this will be done very soon.

Yes. C47 will always be the retrofit DM42/DM42n option, which requires only a bezel to be added. R47 runs the same software with a handful of menu changes due to the keyboard changes. Programs are interchangeable. State files are interchangeable.

The team members are listed in the calculator's INFO menu under WHO?

SwissMicros GmbH provides the platform for C47 in the form of the DM42 and DM42n calculators and fully supports the installation of third party firmware like ours and also is in support of the development of the dedicated R47 calculator.

The user community provides some support in the form of contributing code, Wiki descriptions, problems and solutions, examples, bug reports and feature requests.