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

Question

My files are

// main.c  

#include <ClasseAusiliaria.c>

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

and

// add.c  

int add(int a, int b) {
    return a + b;
}

Answer 1

Use double quotes #include "ClasseAusiliaria.c" [Don't use angle brackets (< >) ]

And I prefer to save the file with .h extension In the same directory/folder.

TLDR: Replace #include <ClasseAusiliaria.c> with #include "ClasseAusiliaria.c"