GeoGebra - the world’s favorite, free math tools used by over 100 million students and teachers
Interactive Open Source Numerical Library of C/C++ functions for Engineering, Finance, Maths, Science and Statistics. With Online Calculators for Numerical Components and Excel Add-ins.
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Online GDB is online compiler and debugger for C/C++. You can compile, run and debug code with gdb online. Using gcc/g++ as compiler and gdb as debugger. Currently C and C++ languages are supported.