Standard file formats
RFC 678

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Network Working Group                                          J. Postel
Request for Comments:  678                                     (SRI-ARC)
NIC:  31524                                             19 December 1974

                         Standard File Formats

Introduction

   In an attempt to provide online documents to the network community we
   have had many problems with the physical format of the final
   documents. Much of this difficulty lies in the fact that we do not
   have control or even knowledge of all the processing steps or devices
   that act on the document file. A large part of the difficulty in the
   past has been due to some assumptions we made about the rest of the
   world being approximately like our own environment. We now see that
   the problems are due to differing assumptions and treatment of files
   to be printed as documents. We therefore propose to define certain
   standard formats for files and describe the expected final form for
   printed copies of such files.

   These standard formats are not additional File Transfer Protocol data
   types/modes/structures, but rather usage descriptions between the
   originator and ultimate receiver of the file. It may be useful or
   even necessary at some hosts to construct programs that convert files
   between common local formats and the standard formats specified here.

   The intent is that the author of a document may prepare his/her text
   and store it in an online file, then advertise that file by name and
   format (as specified here), such that interested individuals may copy
   and print the file with full understanding of the characteristics of
   the format controls and the logical page size.

Standardization Elements

   The elements or aspects of a file to be standardized are the
   character or code set used, the format control procedures, the area
   of the page to be used for text, and the method to describe
   overstruck or underlined characters.

   The area of the page to be used for text can be confusing to discuss,
   in an attempt to be clear we define a physical page and a logical
   page. Please note that the main emphasis of this note is to describe
   the standard formats in terms of the logical page, and that it is up
   to each site to map the logical page onto the physical page of each
   of their devices.

                                 - 1 -


                                                   Standard File Formats
                                                Standardization Elements

      Physical Page

         The physical page is the medium that carries the text, the
         height and width of its area are measured in inches.

            The typical physical page is a piece of paper eleven inches
            high and eight and one half inches wide.

               Typical print density is 10 characters per inch
               horizontally and 6 characters per inch vertically. This
               results in the typical physical page having a maximum
               capacity of 66 lines and 85 characters per line. It is
               often the case that printing devices limit the area of
               the physical page by enforcing margins.

      Logical Page

         The logical page is the area that can contain text, the height
         of this area is measured in lines and the width is measured in
         characters.

            A typical logical page is 60 lines high and 72 characters
            wide.

   Code Set

      The character encoding will be the network standard Network
      Virtual Terminal (NVT) code as used in Telnet and File Transfer
      protocols, that is ASCII in an eight bit byte with the high order
      bit zero.

   Format Control

      The format will be controlled by the ASCII format effectors:

         Form Feed       <FF>

            Moves the printer to the top of the next logical page
            keeping the same horizontal position.

         Carriage Return <CR>

            Moves the printer to the left edge of the logical page
            remaining on current line.

                                 - 2 -


                                                   Standard File Formats
                                                Standardization Elements

         Line Feed       <LF>

            Moves the printer to the next print line, keeping the same
            horizontal position.

         Horizontal Tab  <HT>

            Moves the printer to the next horizontal tab stop.

               The conventional stops for horizontal tabs are every
               eight characters, that is character positions 9, 17, 25,
               ... within the logical page.

            Note that it is difficult to enforce these conventions and
            it is therefore recommended that horizontal tabs not be used
            in document files.

         Vertical Tab    <VT>

            Moves the printer to the next vertical tab stop.