8.5

8.5/three_files/func.c

+#include "func.h"
+
+int func1(int a)
+{
+	return (a * 10);
+}
+
+int func2(int a)
+{
+	return (a * 2);
+}
\ No newline at end of file

8.5/three_files/func.h

+#pragma once
+#define DF(a) ((a)*(a))
+extern int func1(int x);
\ No newline at end of file

8.5/three_files/main.c

+#include <stdio.h>
+#include "func.h"
+
+int func_name_or_id()
+{
+#ifdef PRINT_ID
+	printf("201920756");
+	return 0;
+#else
+	printf("");
+	return 1;
+#endif
+}
+
+int main()
+{
+	func_name_or_id();
+}