How to invoke function from external .c file in C?

Question

My files are

// main.c  

#include \"add.c\"

int main(void) {
    int result = add(5,6);
    printf(\"%d\\n\", result);
}  

and

Answer 1

make a file classAusiliaria.h and in there provide your method signatures.

Now instead of including the .c file include this .h file.