This is ReactOS Calc, a scientific calculator for Win32 and Win64 systems.
I decided to start this project because the winecalc wasn't very usable (it's just my personal opinion) and the calculator included into Win95 and Win98 has some big limitations, like the missing support for 64 bit integers.
The user interface of ReactOS Calc is really similar to Microsoft calculator, so you should be able to use this replacement very quickly.
COMPILATION
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You need MinGW for compiling ReactOS Calc.
Just launch MAKEALL.BAT from the source directory.
This will generate all executables for various configurations and platforms.
COMPILING THE HELP FILE
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ReactOS Calc uses HTMLHELP for opening the help file and generating the popups.
The Microsoft HTMLHELP Workshop is freely downloadable from Microsoft's site at:
Unfortunately, I'm not very good at writing user's manuals.
Although ReactOS Calc is pretty simple and I still think you should be able to understand the basic operations yourself, a good manual would be a nice presentation for new users.
Then, the next step is the translation into other languages.
If you would like to help in some way on these tasks, you are welcome.