Now in this section, we will create a folder to contain some extra files. 1- How to compile those files. 2- We will create a separate folder to contain the obj files. 3- We will create a separate folder to the output executable as well. Will create a folder called "api" inside the source folder: this folder will contain: mmath.h #ifndef _MMATH_H_ #define _MMATH_H_ double Add(int a, int b); #endif mmath.c #include "mmath.h" double Add(int a, int b) { return a+b; } Let's update out main as well... main.c #include <stdio.h> #include "api/mmath.h" int main(int argc,char *argv[]) { double res = Add(23,26); printf("You see, u see this... I'm running\r\n"); printf("%f\r\n", res); printf("Externals Executed\r\n"); return 0; } Now How to compile this? We need to include our custom header file as well while compiling and we also need ...