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_R4Ptype(vector_R4P)::pt(1:2)real(R4P)::apt(1)=ex_R4Ppt(2)=ey_R4Pa=angle_R4P(pt(1),pt(2))print"(F4.2)",aendprogram volatile_doctest