[COFF] Building OS from source in the olden days

I'm currently reviewing a paper about Unix and Linux, and I made the comment that in the olden days the normal way to build an OS image for a big computer was from source. Now I've been asked for a reference, and I can't find one! Can anybody help? Greg -- Sent from my desktop computer. Finger grog(a)lemis.com for PGP public key. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft mail program reports problems, please read http://lemis.com/broken-MUA