I'm afraid I have to apologise for a blunder on my part or a forum error. I 'moved' a post to here from OS Design and Theory about .o and .obj object file formats - the original question asked 'What format is an .o file in?'.
Unfortunately, when I looked, the moved topic had not appeared in this forum. I am trying to get it reinstated now. Apologies to OP. Needless to say, I am feeling highly guilty
Cheers,
Adam