cvs tag -b [new branchname]
Finish changes to the working directory, then
cvs commit
Example branching at revision tag ''R1'':
cvs -d /mnt/data/CVSHOME co -r R0_3_3 miav
cd miav
cvs tag -b stable_0_3
# do some changes in the code
cvs commit -m"Made a change in a branch"