RFC 387 (rfc387) - Page 1 of 5

Some experiences in implementing Network Graphics Protocol Level 0

Alternative Format: Original Text Document
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Network Working Group                                  Karl C. Kelley
Request for Comments:  387                                Jaacov Meir
NIC:  11359                                                   8/10/72
Categories:  D.6, F
Obsoletes:
References:  RFC #292


   SOME EXPERIENCES IN IMPLEMENTING NETWORK GRAPHICS PROTOCOL LEVEL 0


    We are in the process of implementing NGP-0 at several hosts.  For
the time being, we are forced to consider the remote host as the "last
intelligent machine". We are attempting to translate NGP-0 to a machine
dependent code for the Computek display. The remote hosts are CCN, UCSD,
and soon RANDCSG. More comments about that work will be made in
subsequent RFC's. The concern of this RFC is twofold:

    1.  Clarify the coordinate number system.

    2.  Puzzle over how to do TEXTR string without either:

        a.  Reading current position and saving it while the text string
            is being output, or

        b.  Monitoring the beam position for each NGP command and saving
            this information somewhere.

    An appendix to this RFC will outline the conversion from the NGP
coordinate system to the floating point arithmetic on the PDP-1O.

The Coordinate Data

    The document for NGP-0 (RFC 292) does not say specifically that the
format of coordinate data is the same whether the command is in absolute
or relative mode. The only thing stated is that they are in two's
complement notation with the leftmost bit being the sign bit.  It is
possible to use two different 2's complement schemes:













Kelley & Meir
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