An update to isCOBOL is generally made available in a platform independent .zip file.
For example isCOBOL-546-9-15DEC2009(2009SP2update).zip contains build 546.9 which is the first update after the 2009 SP2 release which was build 546.8.
After extracting the files from the archive you will see a VersionHistory.txt file in the lib folder. This file lists the features preceded by a plus sign and the corrections preceded by a minus sign. For example:
+ functions DATE-TO-YYYYMMDD, DAY-TO-YYYYDDD and YEAR-TO-YYYY are now supported
+ new routine W$KEYBUF is available. Op-codes 1, 2, 3 and 9 are now supported.
- opening .chm file with $WINHELP routine caused error if there are trailing spaces in its name