Hello and welcome to the forum,
UNSTRING is used to break a variable into smaller pieces. Most times unstring is used to compound delimited data (string) into multiple individual fields.
Here is the link to the cobol reference manual which completely explains unstring:http://publibz.boulder.ibm.com/cgi-bin/ ... r10/6.2.39
Suggest you bookmark the link as this manual contains the complete language reference.