 ensure_loaded(:File)
ensure_loaded(:File)With this semantics, we hope to get as close as possible to the clear semantics without the presence of a module system. Applications using modules should consider using use_module/[1,2].
Equivalent to load_files(Files, [if(not_loaded)]).57On 
older versions the condition used to be if(changed). Poor 
time management on some machines or copying often caused problems. The make/0 
predicate deals with updating the running system after changing the 
source code.