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Network Working Group                                           R. ReddyRequest for Comments: 320                                            CMUNIC: 9350                                                  27 March 1972Workshop 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]