Xerox Corporation

Butler W Lampson

Ronald E Rider

Charles Patrick Thacker

David R Boggs

Robert M Metcalfe

Eric E Schmidt

Robert F Sproull

Severo M Ornstein

James Y Leung

A software version management system, also called system modeller, provides for automatically collecting and recompiling updated versions of component software objects comprising a software program for operation on a plurality of personal computers coupled together in a distributed software environment via a local area network. The component software objects include the source and binary files for the software program, which stored in various different local and remote storage means through the environment. The component software objects are periodically updated, via a system editor, by various users at their personal computers and then stored in designated storage means. The management system includes models which are also objects. Each of the models is representative of the source versions of a particular component software object and contain object pointers including a unique name of the object, a unique identifier descriptive of the cronological updating of its current version, information as to an object's dependencies on other objects and a pathname representative of the residence storage means of the object. Means are provided in the system editor to notify the management system when any one of the objects is being edited by a user and the management system is responsive to such notification to track the edited objects and alter their respective models to the current version thereof.

Software version management system

An electronic image processing system includes a controller for receiving character font data from a main memory and for converting it to image data utilizable by a raster output device capable of formatting the image data in a plurality of scan lines onto an imaging medium. The controller includes an input memory coupled to the main memory for receiving character font data therefrom, a data pattern memory for providing a predetermined pattern of data in response to a predetermined address signal, and a plurality of band buffer memories each capable of storing image data representing a predetermined number of scan lines constituting an image band, each band buffer memory having enable input lines and associated data input lines. The input memory is addressed to access character font data therefrom, such accessed character font data being then applied to respective enable input lines of a selected one of the band buffer memories. The predetermined address signal is applied to the data pattern memory in order to access the predetermined pattern of data and apply same to respective data input lines of the selected band buffer memory. Additionally, the selected band buffer memory is addressed to load into an addressed memory location the predetermined pattern of data only with respect to those data lines whose associated enable input lines are enabled by the character font data.

Electronic image processing system

System and method for parallel decoding of character data in run length format to produce data in dot matrix form for presentation to a display device. The data for successive runs is stored in registers and processed in parallel to provide address data for memory devices programmed to deliver predetermined output data patterns in response to the address data.

Parallel run-length decoder

High resolution character generator for producing rows of characters to be scanned on a display medium. Input data defining characters to be printed in ordered rows of text is sorted to provide specifications for the characters which being on each successive scan line. These specifications are stored initially in an input buffer, and specifications for characters which have been partially printed in a previous scan line are stored in an active character buffer. For each scan line, the character specifications are read first from the active character buffer and then from the input buffer until an end of line specifier is reached. For each character specification received, a font memory containing data defining the characters is cycled. The data from the font memory is decoded and presented to the display medium on a line by line basis.

High resolution character generator

Apparatus for enabling communications between two or more data processing stations comprising a communication cable arranged in branched segments including taps distributed thereover. Tied to each tap is a transceiver which on the other side connects to an associated interface stage. Each transceiver includes, in addition to the usual transmitter and receiver sections, a gate which compares the data from the interface stage with the data on the cable and indicates whether such are equal. Should such be unequal, an interference between the transceiver and the cable is indicated, disabling the associated transmitter section. Each interface stage tied to such transceiver also includes an input and an output buffer on the other end thereof interfacing with a using device, such input and output buffers storing both the incoming and outgoing data. The output buffer is connected to a clock-driven shift register which converts the buffered data to a serial stream, feeds such data to a phase encoder, which then connects to the transmitter or driver section of the transceiver. The input buffer is loaded by an input shift register which derives its clock from a phase decoder, the shift register and the phase decoder both connecting to the receiver section. When the station is to start transmitting, the phase decoder detects the presence of other transmissions on the cable and detains the output shift register until no other transmissions are sensed. Once a transmission has begun, if interference is detected and the transmitter section is disabled, a random number generator is used to select an interval of time at the completion of which the next attempted transmission will take place. Concurrently, a counter counts the number of interferences, or collisions, which recur in the attempted transmissions of one data packet and weights the mean of the random number generator accordingly. The input shift register is also connected to an address decoder which enables data transfer to the input buffer only during those times when the data is preceded by an appropriate address.

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Portola Valley, CA, United States of America

Butler W Lampson