alt Hacker NewsIn line printers, a line feed moves the paper forward one line. A carriage return moves the print head back to the start of a line. You can do interesting things by making them separate commands, like bold text (overstrike) or underlining, so they were independent commands for talking to a line printer.
ASCII standardized on a character set containing control codes for line printers, so it included CR and LF separately. It's a bit weird that some terminals changed the semantics of those control codes, but I guess things never stay static in time.
Line printers (also "chain printers" from IBM) used "form feed" to move the paper to the next "form", which for the most part was moving the tractor fed paper to the line after the page perforations.
The printers either kept track of the number of lines printed "so far", or, in the case of a chain printer, there was a literal chain (similar to an engine timing belt) that had a particular location that was supposed to be aligned with the paper perforation.
Standard tractor feed paper had a printable area that was 132 monospaced characters wide (13.2") and 11" high. Tractor feed paper had the holes at a standard distance apart vertically and a standard margin to allow for the tractor holes and an area before printing, so that the paper could also have vertical perforations to remove the tractor feed paper after printing.
Teletypes were 72 characters wide and 0.1" line height and used continuous paper rolls.