Unlike many other modern operating systems, UNIX was not written by a single monolithic development team. It started out as a research operating system, and its power came from the creativity of hundreds of brilliant programmers solving the problems they came across in their work. After writing a new tool, they'd typically write a reference document (a "man page"), and if the tool was significant, a technical paper describing its use.
For years, the technical papers (or "supplementary documents" as they have now come to be called) were the only tutorial documentation for many UNIX programs. Now, some of these papers have been superseded by in-depth books on individual programs.
However, for many programs, the Supplementary Documents remain the single, authoritative source for detailed documentation.
This volume, the User's Supplementary Documents, collects papers relating to miscellaneous "user" tools, principally text editors and document processors.
"Sometimes, when I'm stuck with a problem, I still go back to the original UNIX papers. They are terse, but often incredibly precise. Sometimes, a careful re-reading reveals some nuance that makes all the difference." --Tim O'Reilly