Joined: 06 Jun 2008 Posts: 8154 Location: East Dubuque, Illinois, USA
The Enterprise COBOL V6.1 Language Reference manual is at http://publibfp.boulder.ibm.com/epubs/pdf/igy6lr10.pdf and page 264 gives the syntax diagram for class conditions. The syntax diagram makes it very clear that the IS can be part of the statement or not -- programmer's choice.
Bookmark this reference manual -- if you use it before posting you will resolve most of this type of question without needing to post anything. This IS an expert's forum and you are expected to be able to do your own research BEFORE posting a question.