In addition to what has already been said, CODE tags use a fixed width font. So text like:
which looks like very different line lengths without CODE tags, clearly show that they contain the same number of characters when that same text is displayed using CODE tags:
And, if your code or data contains tab characters, those tabs are preserved if you copy and paste text from regions of a post that are tagged by CODE or ICODE tags, but copy as spaces when not tagged.
So, yes: always use code tags for full line sample code, input, and output; and use icode tags for partial line, imbedded sample code, input, and output!