and one more thing, i have made the changes EXTRENALLY... i.e. by goging manually to that file and making changes (appeding) to that file...
In order to compare any file contents between previous and current snapshot , you need to check the "Contents" parameters for the "FILE" asset/part in the snapshot job.
Once this option is enable , you will be able to compare the contents.
Thanks & Regards,
thanks a lot Gauri, it worked.