cvs - show differences between revisions/releases

To show the differences between two file revisions:

$ cvs diff -kk -u -r 1.14 -r 1.15 file.c

To show the differences between two tagged versions/releases of the project (in each of the files):

$ cvs diff -r RELEASE_1_0 -r RELEASE_1_1

A context diff between two releases redirected to the file:

$ cvs diff -c -r RELEASE_1_0 -r RELEASE_1_1 > diffs