Please when you enter a value for "x", don't use "," but "." when you need to enter a float number (ex: 4,1 -> 4.1) !! Source code: How to compile it ? -> compile the "Equation.c" file with gcc, to install gcc just type: "sudo apt update && sudo apt install gcc -y" on a terminal, if you use Windows, install mingw32 and add the "bin" folder to your environment variable. Ho to edit the code ? -> just open the "Equation.c" with any text editor such as Sublime Text or notepad etc.... . ENJOY !