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 vecfor_R16Ptype(vector_R16P)::pt(1:2)real(R16P)::apt(1)=ex_R16Ppt(2)=ey_R16Pa=angle_R16P(pt(1),pt(2))print"(F4.2)",aendprogram volatile_doctest