## Description of the "Blackboard" Calculator

Briefly:

- The "Blackboard" calculator for OS Windows is a very simple programming environment that allows you to organize calculations using cycles and branch operators. This makes it possible to numerically solve algebraic and differential equations, approximate certain integrals, sum series, etc. Almost all algorithms of computational mathematics can be implemented.
- On the other hand, the "Blackboard" calculator can be used simply as a convenient multiline formula calculator, which does not require any mathematical knowledge, is suitable for household, accounting, engineering, etc.

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- Formulas in the calculator window are typed using the standard keyboard and do not contain any characters that are absent on it. But even under this condition, the writing of formulas is quite close to mathematical. So, for example, the module sign has the form "||", functions are applied to numbers without functional brackets, for example, sin0.1, and round "()", square "[]" and curly "{}" brackets are available to determine the order of arithmetic operations. To increase the speed of a set of formulas, templates of elementary functions are provided.
- You can simultaneously count several formulas, possibly related to each other. The latter means that quantities determined by some formulas can participate in other formulas. The simplest example: if a certain parameter is repeatedly included in the calculated expressions, then, having determined it with a separate formula, new parameter values can be enterule only in this one place.
- Formulas can be commented and saved to a file for future use. Thus, you can create a library of your programs, for example, for accounting or to fill out a tax return.
- The calculator allows you to organize loops like while-wend, do-until and branch operators if-elseif-else-endif. And also use the continue and break keywords in loops. There are tools for debugging computational formulas.
- The sequences of values obtained in the process of cyclic calculations are automatically displayed in the form of graphs. Thanks to the
*CanvasJS library*, these graphs are interactive: they can be stretched to reveal small details, displaced along the horizontal axis for the same purpose, and, if there are several graphs, hide unnecessary ones. - In order to start using the "Blackboard" calculator as a simple calculator, it is enough to spend one or two minutes reading the first part of the attached help file. For users who are familiar with the basics of programming, it takes the same amount of time to view the second part, which is intended for beginners. Studying a small number of syntax rules is facilitated by the fact that the calculator displays detailed error messages.
- The program interface is more than simple: in addition to standard controls and field for setting the number of fractional decimal places, there are only three buttons:
- "Start" - starts the calculation.
- "Stop" - stops calculations, which can then be continued again by the "Start" button. Pressing the "Stop" button again clears the memory so that the count can be started from the very beginning.
- "Function Templates" and "Keywords" are simply lists of templates to speed up a set of formulas.