C-ISAM and S.E.

Warning: Novice 101 question Are S.E. files just C-ISAM files with a null primary key? I have a program that reorganizes C-ISAM files and am wondering if I use it to reorg a S.E. file can I expect trouble. Essentially, could you (do you) use BCHECK on S.E. files or is there a different INFORMIX command. Thanks, Glen Johnson