# File ## .exe The file that can be executed , this is the so-called program . ## .c .c file contains the **main** function and can be compiled to become an .exe file . ## .h .h file is the tool box of .c , it can contain functions , structures , global variables .....etc . The only diffrence between .c and .h is that .h don't contains **main** . .h file is often be used as a big function box , with many useful functions . ```graphviz Digraph G{ node[shape = box ] ".c" -> ".exe" ".h" -> ".c" } ``` ## Common Format for .c ```clike= #include <stdio.h> int main(){ operation ; return 0 ; } ``` The .h above can be any , depends on the funtion you wish to call .