Routines are given long, expressive, mixed-case names that hopefully give both user and developer a good idea what each routine does. This aspect of coding style is the second most important factor in making code readable, understandable, and maintainable (the most important being plentiful and detailed comments, of course).
The first three characters of each routine name are JT_. This helps ensure uniqueness and avoid conflicts with names of user or system routines. Filenames omit these characters.
Routines that perform operations specific to a storage format have a descriptive string appended to the name. For example, the names of all routines that perform operations specific to matrices stored in the ELLPACK-ITPACK format (known as ``primary format'' in NSPCG) end with the characters _ELL.