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rfc:rfc678

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. 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.
  1. 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.
             The conventional stops for vertical tabs are every eight
             lines starting at the first printing line on each logical
             page, that is lines 1, 9, 17, ... within the logical
             page.
          Note that it is difficult to enforce these conventions and
          it is therefore recommended that vertical tabs not be used
          in document files.
       Back Space      <BS>
          Moves the printer one character position toward the left
          edge of the logical page.
    Not all these effectors will be used in all format standards, any
    effectors which are not used in a format standard are ignored.
 Page Length
    The logical page length will be specified in terms of a number of
    lines of text.
  1. 3 -
                                                 Standard File Formats
                                              Standardization Elements
 Page Width
    The logical page width will be specified as a number of
    characters.
 Overstriking
    Overstriking (note that underlining is a subset of overstriking)
    may be specified to be done in one or both of the following ways,
    or not at all:
       By Line
          The composite line is made up of text segments each
          terminated by the sequence <CR><NUL> except that the final
          segment is terminated by the sequence <CR><LF>.
       By Character
          Each character to be overstruck is to be immediately
          followed by a <BS> and the overstrike character.
 End of Line
    The end of line convention is the Telnet end of line convention
    which is the sequence <CR><LF>. It is recommended that use of <CR>
    and <LF> be avoided in other than the end of line context.
  1. 4 -
                                                 Standard File Formats
                                                      Standard Formats

Standard Formats

 Format 1 [Basic Document]
    This format is designed to be used for documents to be printed on
    line printers, which normally have 66 lines to a physical page,
    but often have forced top and bottom margins of 3 lines each.
       Active Format Effectors
          <FF>, <CR>, <LF>.
       Page Length
          60 lines.
       Page Width
          72 Characters.
       Overstriking
          By Line.
 Format 2 [Terminal]
    This format is designed to be used with hard copy terminals, which
    in the normal case have 66 lines to a physical page. It is
    expected that there are no top or bottom margins enforced by the
    terminal or its local system, thus any margins around the physical
    page break must come from the file.
       Active Format Effectors
          <FF>, <CR>, <LF>, <HT>, <VT>, <BS>.
       Page Length
          66 lines.
       Page Width
          72 Characters.
       Overstriking
          By Character.
  1. 5 -
                                                 Standard File Formats
                                                      Standard Formats
 Format 3 [Line Printer]
    This format is designed to be used with full width (11 by 14 inch
    paper) line printer output.
       Active Format Effectors
          <FF>, <CR>, <LF>.
       Page Length
          60 lines.
       Page Width
          132 Characters.
       Overstriking
          None.
 Format 4 [Card Image]
    This format is designed to be used for simulated card input. The
    page width is 80 characters, each card image is followed by
    <CR><LF>, thus each card is represented by between 2 and 82
    characters in the file. Note that the trailing spaces of a card
    image need not be present in the file, and that the early
    occurence of the <CR><LF> sequence indicates that the remainder of
    the card image is to contain space characters.
       Active Format Effectors
          <CR>, <LF>.
       Page Length
          Infinite.
       Page Width
          80 Characters.
       Overstriking
          None.
  1. 6 -
                                                 Standard File Formats
                                                      Standard Formats
 Format 5 [Center Document]
    This format is intended for use with documents to be printed  on
    line printers which normally have 66 lines to the physical page
    but enforce top and bottom margins of 3 lines each. The text is
    expected to be centered on the paper. If the horizontal printing
    density is 10 characters per inch and the paper is 8 and 1/2
    inches wide then there will be a one inch margin on each side.
       Active Format Effectors
          <FF>, <CR>, <LF>.
       Page Length
          60 Lines.
       Page Width
          65 Characters.
       Overstriking
          By Line.
 Format 6 [Bound Document]
    This format is intended for use with documents to be printed  on
    line printers which normally have 66 lines to the physical page
    but enforce top and bottom margins of 3 lines each. If the
    horizontal printing density is 10 characters per inch and the
    paper is 8 and 1/2 inches wide then the text should be positioned
    such that there is a 1 and 1/2 inch left margin and a one inch
    right margin.
       Active Format Effectors
          <FF>, <CR>, <LF>.
       Page Length
          60 Lines.
       Page Width
          60 Characters.
       Overstriking
          By Line.
  1. 7 -
                                                 Standard File Formats
                                            Implementation Suggestions

Implementation Suggestions

 Overflow
    Overflow can result from two causes, first if the physical page is
    smaller than the logical page, and second if the  actual text in
    the file violates the standard under which it is being processed.
    In either case the following suggestions are made to implementors
    of programs which process files in these formats.
    Length
       If more lines are processed than fit within the minimum of the
       physical page and the logical page length since the last <FF>,
       then the <FF> action should be forced.
    Width
       If more character positions are processed than fit on the
       minimum of the physical page width and the logical page width
       since the last <CR>, then characters are discarded up to the
       next <CR>.
       or
       If more character positions are processed than fit on the
       minimum of the physical page width and the logical page width
       since the last <CR>, then the <CR> and <LF> actions should be
       forced.

References

 A. McKenzie "TELNET Protocol Specification," Aug-73, NIC 18639.
 "USA Standard Code for Information Interchange," United States of
 America Standards Institute, 1968, NIC 11246.
  1. 8 -
/data/webs/external/dokuwiki/data/pages/rfc/rfc678.txt · Last modified: 1992/10/15 21:53 by 127.0.0.1

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