During my studies (several years ago), I discovered the Equation solver TkSolver. Some days ago, I was trying to find a GNU equivalent to TkSolver as I wanted to perform some computations. My searches were unsuccessful (not exactly but I didn’t find a similar tool) but I found Eureka Solver which is an old solver (may be the first of this type).

Eureka Solver (and TK solver) is build on the declarative programming approach while the “standard” solvers use a procedural approach.

The declarative programming has a great interest when you have to solve multiple related equations because you will express the problem without consideration of the flow. The user has to write the equations and it is all. The software will compute a solution (or several) in regard to the inputs. The user does not need to consider the fact that parameters *x* shall be computed before parameters *y *nor to consider the fact the formula* F* has to be injected in the formula* F1 *before computation of F1…

The declarative programming is a very good tool for engineers (mixing equations), finances (find the optimized solution,…) people without software development or heavy mathematical skills. With the declarative approach, the user focus on the *What* and not on the *How*.

## Eureka Solver

Eureka was an equation solver produced by Borland in the 1980s. It ran under DOS (16bits). The author, Roger Schlafly, proposes to download and use Eureka as freeware for personal or educational use.

As the author says: “the program is rather dated”. It is true, the interface looks 80’s / 90’s, it runs with limited graphics,… and you need a DOS emulator (I use DosBox) to run it on a “modern” computer.

Several websites (i.e. bitsavers.org) propose the pdf version of the Eureka The Solver Owners Handbook. You can search on the web about “Eureka_The_Solver_Owners_Handbook_1987” to find this book.

Eureka could support some derivative equations but it is clearly not its force, don’t explicitly try to solve differential equation with him, it can’t.

In conclusion, for hobbyist and day to day use, it is sufficient for it the user disregards the 90’s old interface and the not opensource. If you want a more advanced free tool, you can check Maxima and the OpenModelica.

## Installation and use

The installation is really straightforward. Just download Eureka from Eureka Solver website and unzip in an appropriate directory. I recommend using a simple access directory (i.e. C:\Eureka), as we will have to mount this directory in DOSBox.

Install DosBox from the official website and launch it.

In DosBox, you will have to mount the Eureka directory. Just do it by “mount C C:\Eureka” if you set Eureka in your C:\Eureka folder.

Then, just navigate to the C directory by typing “C:” and launch Eureka thanks the command “eureka”.

If you have some troubles, you can use the command “dir” to consult the content of your directory…

Eureka is an old design tool. You can access the top menu by pressing “Esc” on your keyboard and use the left right up down keys to navigate inside the menus.

You can use some shortcut to navigate (i.e Alt+E to Edit, Alt+S to Solve…). As there are not some many commands, it is very easy to navigate and understand the menus organization.

For the advanced functions, you can consult the book Eureka The Solver Owners Handbook. It will give you several tips and examples.

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