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.
Source Code
program volatile_doctestuse penfuse penfinteger::uopen(newunit=u,status='scratch')call penf_print(u)close(u)print"(A)",'done'endprogram volatile_doctest