Here is the PDF file for the notes from which Berkeley's Math 245A, "General Theory of Algebraic Structures", is taught. (In looking at this, you might occasionally catch it at a moment when it is being revised, and something has gone wrong. If that happens, look at the next-to-last version.) A published version will appear soon as a Springer Universitext.
If you have any corrections or comments, you can e-mail me: .
I maintain lists of answers to some questions submitted by students over the course of the semester. Here is the list from Spring 2014, and here is a similar list from Spring 2008 and Fall 2011. The pagination has changed from year to year as I revise the material. When I have some time, I hope to fuse these files, and give page-references matching the published version.