Add function and o.h, o.c for testing function

tests/o.c

@@ -0,0 +1 @@
+#include ""

tests/o.h

@@ -0,0 +1,3 @@
+void print(char *text)
+void println(char *text)
+

tests/work1.c

@@ -105,3 +105,7 @@ void display_menu() {
     printf("\n");
     read_file("./../note/section1.txt");
 }
+
+void display_students() {
+    printf()
+}