# Finding Information about Class Level Commands [duplicate]

Possible Duplicate:
Documentation reference for LaTeX internal commands?

I'm working on writing a company-specific class file for reports in LaTeX and I thought I would start by reading report.cls. I'm having a difficult time finding concise definitions of the commands/macros available in class file writing. For example, what does \p@ do? What about \@plus? Where is \@compatibility defined?

A \documentclass is loaded after some default LaTeX commands, defined in a combined source called latex.ltx (this is in addition to the roughly 900 TeX primitives and macros loaded/defined by default). Some of the macros defined in latex.ltx is done for the sake of brevity and/or consistency, like:
\newdimen\p@ \p@=1pt % this saves macro space and time

For what it's worth, and as future reference, consider browsing through the "unpacked LaTeX catalogue on CTAN". latex.ltx is mostly built up from the sources lt*.dtx. When viewing latex.ltx, each reference used is clearly marked by the original source.