Today we take it for granted that computers can set type, but from the 60s to the 80s, most computers used either teletypes or character-based screens. The Xerox Star and Apple Lisa and Apple Macs, and PostScript changed this, but before them, typesetting was done using weird command languages that would send pages to special typesetters. The most well known setup was troff, which lives on in groff and in Solaris. The troff system used a computer typesetter called a CAT, and it wasn't a bitmap laser printer. It has these fonts that were spools of film that were photographs of letters. The font sizes were created by projecting the image of the letter onto the page at different sizes. I believe the rest of the process was like a photocopier - the toner goes on, and then is transferred to the paper, and fused.