Xerox Paris, a document system Support & Software 用户指南

Carriage-return and line-feed functions are important because they define the basic
unit of data for the PARIS Designer, that is, a line.

A collection of lines forms a page, which in turn needs to be terminated. To achieve
this and to make print data more efficient, many systems make use of a third special
character to terminate pages, a form-feed.

In simple terms, form-feeds are just a ‘super’ line-feed and are usually employed as
a replacement of the line-feed in a carriage-return/line-feed pair. Therefore the last
line on a page is quite often terminated with a carriage-return, form-feed pair of
bytes.

Form-feeds are not as vital as carriage-return and line-feed functions because most
pages are terminated after a given amount of lines (for example 66 lines per page).
However, this implied page end becomes inefficient in cases where only a few lines
are to be printed on a given page, and to make up the 66 required lines, a set of
blank lines (a series of carriage-returns and line-feeds with no characters on them)
will need to be sent.

Some print files use form feeds while others rely on a fixed number of lines to
achieve page ends. If your data does make use of form-feeds you will need to make
sure that your input filter is set correctly (refer to the section 

Function on page 77).