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Technique for a Plurality of Word Processing Terminal Sharing a Single Printer

IP.com Disclosure Number: IPCOM000048279D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Barnes, JG: AUTHOR [+3]

Abstract

In word processing technology it has been found to be advantageous for a plurality of display units to share a single printer. Since about 65 percent to 95 percent of the time spent in producing a final hard copy is involved informatting the text to be printed on the hard copy and only 5 percent to 35 percent of the time spent in actual printing, the technology has been moving in the direction of expedients whereby a plurality of display units are multiplexed, i.e., share a single printer. The present approach represents a specific example of such an expedient, and more particularly one directed toward an error recovery capability.

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Technique for a Plurality of Word Processing Terminal Sharing a Single Printer

In word processing technology it has been found to be advantageous for a plurality of display units to share a single printer. Since about 65 percent to 95 percent of the time spent in producing a final hard copy is involved informatting the text to be printed on the hard copy and only 5 percent to 35 percent of the time spent in actual printing, the technology has been moving in the direction of expedients whereby a plurality of display units are multiplexed, i.e., share a single printer. The present approach represents a specific example of such an expedient, and more particularly one directed toward an error recovery capability.

In the system of the present approach, a printer is attached to one station known as the primary workstation and the other stations known as secondary workstations are attached to the primary workstation. All linkages are full duplex bit serial type. Secondaries use the same I/O port to attach to the primary that the primary uses to attach to the printer. Thus the primary workstation controls the printer link doing all error recovery and logging for that link. It also controls the ownership of the printer, maintaining a-first-in, first-out queue for request to use the printer. Any station needing to use the printer must reserve it and wait its turn in the queue to print. When printing is completed, the station must release the printer so that the next station in the queue may begin printing.

In such a system error recovery requires the following capabilities: (1) Automatic "release" of a station that loses power or

has a total link failure while printing.

(2) Automatic retry of all transmission errors.

(3) Redundant maintenance of the print queue by the

secondary stations so that if the Primary

loses power, the queue is maintained. When

powering on, the Primary queries the

Secondaries for any queue status they may have and

restores its queue from their information. This

allows a Secondary that was printing when

the Primary went down to resume printing automatically,

without re-reserving the printer.

This is maintained through the following algorithm. The queue is maintained as a set of three numbers. The Queue Count is the next available position in the queue; the Job Number is the currently active position in the...