Nodes of different colours represent the following:
Solid arrows point from a file to a file which it depends on. A file
is dependent upon another if the latter must be compiled before the former
can be.
program volatile_doctestuse stringifor_string_tuse penftype(string)::astringlogical::test_passed(1)astring=127_I8Ptest_passed(1)=astring%to_number(kind=1_I8P)==127_I8Pprint'(L1)',all(test_passed)endprogram volatile_doctest