Operating system changes that affect language functionality.
example: changes to Windows affecting qBasic functionality,
switch from qBasic to QB64
changes to MAC OS X affecting chipmunk Basic functioning
Language changes that affect program functioning.
example: C++ library changes affecting Asa H functioning
C++ on Linux versus MSWindows
Functionality affected by program growth.
example: Prolog crashing sooner as knowledge base is grown
Adding external disk and/or CD drives to enable continued use of old media.
Backups guarding against media failures.
Porting AsaH to the new tablet computers (and their operating systems).