If someone else has been working on the same files as you have, you may find that there are conflicting modifications. You'll discover this when you try to update your sources.
# cvs update RCS file: LVM/tools/pvcreate.c,v retrieving revision 1.5 retrieving revision 1.6 Merging differences between 1.5 and 1.6 into pvcreate.c rcsmerge: warning: conflicts during merge cvs server: conflicts found in tools/pvcreate.c C tools/pvcreate.c
Don't panic! Your working file, as it existed before the update, is saved under the filename .#pvcreate.c.1.5. You can always recover it should things go horribly wrong. The file named `pvcreate.c' now contains both the old (i.e. your) version and new version of lines that conflicted. You simply edit the file and resolve each conflict by deleting the unwanted version of the lines involved.
<<<<<<< pvcreate.c j++; ======= j--; >>>>>>> 1.6
Don't forget to delete the lines with all the ``<'', ``='', and ``>'' symbols.