I've always used code tags for code but not for showing terminal input and output. I noticed a mod edited one of my threads and now I'm confused as to proper protocol.
Mike
Yes, use them for terminal input and output as well.
It's better than setting random colors and fonts, or labelling them with
----------------output starts here-------------------------
...or letting people guess where it begins and ends.
It's also important because multiple spaces will get compressed in 'normal' text, but are respected within code tags.
This is an "X" with fifteen spaces, then another "X" in normal text:-
X X
This is an "X" with fifteen spaces, then another "X" in code tags:-
X X
It's much better for clarity of indented code and for crucial fixed-width data.
Thanks for asking 
Robin
In addition to what has already been said, CODE tags use a fixed width font. So text like:
iiiiiiiiii
WWWWWWWWWW
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:
iiiiiiiiii
WWWWWWWWWW
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!
It also prevents random sequences of characters from unintentionally becoming smilies.
Yes you should you the code tags for terminal input and output, Recommended!