Sorry for confusing the issue, I meant "hal.h" not "hal.c" as I wrote; it's the .h file where the function is that I'm modifying.
Just to be clear on this, are you saying that ANY file that I modify which is visible in the project, in Project Explorer, will be prompted for saving after modification, not just a .c file ?
I don't think hal.h is in the project folder so that would explain it not being save prompted.