mingw/lib/libmingw32.a(main.o):(.text.startup+0xa0):%2520 undefined%2520 reference%2520to%2520%2560 WinMain@16'

This problem comes when your whole code is commented out and you try to compile the code. The compiler cannot find any of the tokens of C language in this so throws up an error. It searches for the main function as in C & C++ the execution begins from the main function. The main function cannot be found so it returns an error