RFC 177 (rfc177) - Page 1 of 9

Device independent graphical display description

Alternative Format: Original Text Document
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NETWORK WORKING GROUP                                       J. McConnell
Request for Comment: 177           Ames Research Center Moffet Field, CA
Obsoletes: none                                             15 June 1971
Updates: 125
NIC: 7102

           A DEVICE INDEPENDENT GRAPHICAL DISPLAY DESCRIPTION

   As more nodes are connected to the ARPA network, the types of
   graphical display processors available to users is quite varied.  To
   attempt to facilitate the transmission of graphical information over
   the network, a device independent description of a display is
   described.  The using host may make any conversions necessary to
   realize the picture on a specific device.  It is also possible to
   interpose a form machine as proposed by Heafner and Harslem in RFC
   #94.  Some of the items and entities described herein were first
   discussed by Steve Crocker in RFC #86.  It is intended that this
   description is to be oriented to a refresh display with point,
   vector, and character drawing capability, these types of devices
   include the IBM 2250, IMLAC PDS-1, the DEC 338, and DEC 340, as well
   as the Evans and Sutherland LDS-1.  However, direct video storage
   tube devices represented by the ARDS, Tektronix and Computer devices
   can also serve as clumsy interactive devices.  Hard copy devices,
   such as microfilm or plotters, can also be used at the using host's
   discretion.

   There are several items and constructs which will be defined before
   discussing the specifics of the description:

      1.  The network standard graphics description stream (NGDS)
      contains the description, data, and operators necessary to effect
      a display.

      2.  The network standard stream interpreter (NGSI) parses the NGDS
      into its components.

      3.   The network standard display list (NGDL) is the basic entity
      which, when executed, causes graphical information to be
      displayed.

      4.  The network standard list interpreter (NGLI) is the entity
      which executes the NGDL and controls the beam movement to effect
      generation of graphical information.

      5.  The network standard screen (NGS) is the entity on which the
      information is to be displayed.  It may be divided into image
      areas to be defined later.




McConnell
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