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Some experiences in implementing Network Graphics Protocol Level 0 (RFC0387)

IP.com Disclosure Number: IPCOM000003566D
Original Publication Date: 1972-Aug-10
Included in the Prior Art Database: 2000-Sep-13
Document File: 4 page(s) / 8K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

K.C. Kelley: AUTHOR [+2]

Abstract

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:

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 33% of the total text.

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:

System A System B

(Absolute Coordinates) (Relative Coordinates)

-1 -2 -3 -16 0 -1 -2 -15

-2 2 2 ... ...2 -2 2 2 ... 2

+--+--+--+--+---------+--+--+ +--+--+--+--+---------+--+--+

| | | | | | | | | | | | | | | |

+--+--+--+--+---------+--+--+ +--+--+--+--+---------+--+--+

^ ^

.0111 ...............11 = +1/2-e 0.11 ..............11 = 1-e

.00 .................01 = +e 0.100 .............00 = 1/2

.00 .................0 = 0 0.00...............01 = e

.111 ................11 = -e 0.00 ..............00 = 0

.100 ................ = 1/2 1.11 ..............11 = -e

1.10 ..............00 = -1/2

1.00 ..............01 = -1+e = -(1-e)

1.00 ..............00 = -1

-16 -15

Where: e = 2 Where: e = 2

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