The two files caLesson4a.c and caLesson4b.c do exactly the same. The difference is that caLesson4a.c uses EPICS 3.13-style functions which are deprecated in EPICS 3.14. caLesson4a.c compiles with 3.13 and 3.14, caLesson4b.c only compiles with 3.14. To see what has changed try diff caLesson4a.c caLesson4b.c or tkdiff caLesson4a.c caLesson4b.c