What is a reverse line feed

Question

Actually, I googled for a while but without a success. It's just too abstract for me. Anyway, My English is broken. What I want to know is two points as below: What is a reverse line feed? What is the difference between reverse line feed and line feed? So, is there anyone can give me an example or make an explanation? Thank you very much. PS: I'm an invoice here. I don't know whether I made it clear or not for you.

Answer 1

A reverse line feed makes the cursor go back up to the previous line. A regular line feed makes the cursor go to the next line.

Edit: ThePower is correct, these terms originate from the days of line printers, "feed" meaning to feed the paper through the printer, in this case by one line, and reverse line feed moving the paper backwards by one line.

Answer 2

Some earlier computer printers, were able to print subscripts and superscripts, and first did this by rolling up or down a half line, instead of a whole line.

For example, as found in this old printer manual.

Let's take a look at the related vertical commands:

     line feed  and  reverse      line feed, and  
half line feed  and  reverse half line feed


     Line feed goes down one      line.  Reverse goes up one      line.
Half line feed goes down one half line.  Reverse goes up one half line.