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rfc:rfc320

Network Working Group R. Reddy Request for Comments: 320 CMU NIC: 9350 27 March 1972

                Workshop on Hard Copy Line Graphics
 At CMU we have recently interfaced a Xerox Graphic Printer (ex-LDX)
 to the PDP-10 using a PDP-11 as in intelligent controller for the
 printer.  Specially designed interface and data structures permit the
 PDP-11 to generate each scan line as needed without having to resort
 to the brute force generation of the bit image for the whole page.
 The attached pages were produced using this system with the help of a
 document generation program and a character set design program.  This
 is something personal.
 In response to several requests, we are conducting a one day workshop
 on the XCRIBL system.  The workshop will be held in 3124 Science Hall
 at Carnegie-Mellon University on April 12.  An agenda for the
 workshop is attached.  If you are interested in coming or sending
 someone to this workshop, please contact Dr. D. R. Reddy (412-621-
 6200 ext. 149), Mr. Mack Hicks (412-687-5846) or Miss M. Kostkas
 (412-626-2600 ext. 141), for further information or local
 arrangements.  Local reservations may be made at the Webster Hall
 Hotel (412-621-7700) or the Civic Center Motor Hotel (412-683-6700)
 which are within walking distance of Carnegie-Mellon University.

Reddy [Page 1] RFC 320 Workshop on Hard Copy Line Graphics March 1972

                      CARNEGIE-MELLON UNIVERSITY
                 WORKSHOP ON HARD COPY LINE GRAPHICS
                               April 12
                                Morning
               Document Generating Languages and Systems
 9:00-9:30    Raj Reddy          Overview of the XCRIBL system
 9:30-10:20   Joe Newcomer       Languages for Document Generation
 10:20-10:30  Coffee Break
 10:30-12:00  Examples of Document Generation
                            Letter Producing Systems
                            Technical Report Production
                            A Graphics and Gray Scale Image System
                               Afternoon
                            Systems Support
 12:00-1:45  Lunch               Character Sets (Generation and
 1:45-2:45   Lee Erman           Modification)
 2:45-3:00   Coffee Break
 3:00-4:00   George Robertson    The PDP-11 Support System
 4:00-5:00   Bill Broadly and    The PDP-11 XGP Interface (Hardware)
             Jack Wright
                                Evening
                       Session for the "Hackers"
 7:30-10:30  Discussion session of as yet unsolved issues and
             possible hardware-software solutions.

Reddy [Page 2] RFC 320 Workshop on Hard Copy Line Graphics March 1972

                            XCRIBL SYSTEM
                      COMPUTER SCIENCE DEPARTMENT
                      CARNEGIE-MELLON UNIVERSITY
 What you are now reading is a computer printout produced by the
 XCRIBL system.  Computers printers do not have typefaces like this
 one nor can they change typefaces.  Conventional computer printers
 cannot print character sets where the center to center distances are
 not all the same.  The machine that printed this document is a
 facsimile copying machine built by Xerox a number of years ago.  The
 computer science department of Carnegie-Mellon University has
 designed and constructed the interface to connect it to a
 minicomputer (PDP-11) which in turn is linked to a large computer,
 the PDP-10.  The equipment has been working since January.
 The Xerox Graphic Printer (XGP) works in a similar fashion to the
 Xerox office copiers.  Instead of reflecting light off a printed page
 as in a copier the XGP uses a cathode ray tube similar to old
 television tubes as a source of light.  The image is drawn as a
 series of dots on the CRT with a resolution of 12 dots per inch.  The
 line of dots is reflected  onto a selenium drum which
 electrostatically attracts a fine black powder to the exposed
 selenium areas.  The powder is transfered to a moving sheet of paper.
 Finally a fuser melts the powder onto the paper.
 To be able to print any character the pattern of dots which will be
 printed as that character must be entered into the computer along
 with an indicator of what the pattern represents.  To facilitate this
 a program has been written to design character sets.  This program
 draws a grid on a display terminal.  Each box in the grid represents
 one dot in the final Xerox output.  The dots may be set or unset and
 the character redrawn on the display as frequently as one might
 desire.  Because of the ease with which this may be done it becomes
 an enjoyable task to design a character set and then be able to
 change any part of any character.
 The XGP is also capable of drawing lines and gray scale images.  The
 AI group is using the XGP to print pictures of faces and speech
 spectrograms.  The range of possible uses is boundless.
        [This RFC was put into machine readable form for entry]
    [into the online RFC archives by Helene Morin, Via Genie 10/99]

Reddy [Page 3]

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