[redhead]

To sum it all up, Heres what I have left, which isn't exactly giving any clear definition, and thus I assume it is declared in the system dependant header files.

In general:
   savescreen()      -> Need definition
   restscreen()      -> Need definition
   clrscreen()       -> Need definition
   findfile()        -> Need definition
   DeleteFile()      -> Need definition
   WriteString()     -> Need definition
   CenterString()    -> Need definition
   DOSFINDFIRST()    -> Need definition
   DOSFINDNEXT()     -> Need definition
   DOSFINDCLOSE()    -> Need definition
   getmonth()        -> Need definition
   DOSBEEP()         -> Need definition


In message(), Process(), ExecuteProcess(), Scr2_ESSCMD(), 
   Scr3_ESSCMD(), Scr4_ESSCMD(), Scr5_ESSCMD(), main() in mcm10100:
    DOSGETDATETIME() -> Since this takes a struct DateTime
                     I dont kow how that is used, but for
		     starters it can be exchanged with 
		     localtime() found in time.h which takes
		     a struct tm*
		      struct tm
                      {
                          int     tm_sec;         /* seconds */
                          int     tm_min;         /* minutes */
                          int     tm_hour;        /* hours */
                          int     tm_mday;        /* day of the month */
                          int     tm_mon;         /* month */
                          int     tm_year;        /* year */
                          int     tm_wday;        /* day of the week */
                          int     tm_yday;        /* day in the year */
                          int     tm_isdst;       /* daylight saving time */
                       };

In ProcessDailyList() and ExecuteProcess():
   WaitingForTime() -> Can be exchanged with sleep()

In ExecuteEXE():
   DOSEXECPGM()      -> Need definition ( Could be exchanged by execv() or execvp() )

For aadefs.h:
   #include <io.h>
   #include <conio.h>  These are OS dependant, 
   #include <fcntl.h>  and might not be pressent on your
   #include <dos.h>    new compiler environment.
   #include <doscall.h>
   #include <signal.h>
   #include <twindow.h>
   #include <process.h>

Apart from these things, theres also some structures used, but since I first realised them after reading your 9.th post or so, I didn't bother to go back through it all, searching for references..
Once it starts to partly compile, when all the header files issues are solved, it is time to check for things like those.