IFS change not coming into effect

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http://unix.stackexchange.com – I was trying to change the IFS(Internal Field Separator) character to comma for a file processing, but to my surprise the IFS was un-changed. Here's the order of commands and output : mtk4@mtk-laptop:~$ echo .$IFS. . . # A space mtk4@mtk-laptop:~$ IFS="," # No error was thrown, no message mtk4@mtk-laptop:~$ echo .$IFS. . . # Again echo'd it, but no change Please let me know, what is wrong here? (HowTos)