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Multipass Print Technique Using Multiple Printer Tables

IP.com Disclosure Number: IPCOM000039785D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Heath, AW: AUTHOR

Abstract

A method is described to print complex documents requiring printwheel changes (equation printing). Equation printing has long been a problem when the printer has a limited character set. The problem can be summarized by recognizing that printers employing "daisy wheel technology" typically have 96 fully-formed characters which can be printed at any given time. Some accented vowels can be constructed yielding more that 96 actual characters, but for equation printing involving Greek symbols and readable text, the job will typically require two print wheels. The operator is often prompted to change print wheels many times during the printing of a single page, or the printer may not be able to prompt/stop at all, and the operator has no way to change print wheels mid job.

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Multipass Print Technique Using Multiple Printer Tables

A method is described to print complex documents requiring printwheel changes (equation printing). Equation printing has long been a problem when the printer has a limited character set. The problem can be summarized by recognizing that printers employing "daisy wheel technology" typically have 96 fully-formed characters which can be printed at any given time. Some accented vowels can be constructed yielding more that 96 actual characters, but for equation printing involving Greek symbols and readable text, the job will typically require two print wheels. The operator is often prompted to change print wheels many times during the printing of a single page, or the printer may not be able to prompt/stop at all, and the operator has no way to change print wheels mid job. The Displaywriter attempted to solve the problem by doing a special version of the product (PRPQ) which required a product code change and thus the customer must buy the limited support product. This PRPQ would ask the operator which printwheel they wanted to use to print the entire job with, and then proceeded to format the document in such a way that only the graphics on that particular printwheel were printed; lines and pages that did not have any graphics on that printwheel were compressed out and the space skipped over. After printing one pass, the operator would reinsert the same paper into the printer and reprint the job, this time asking for another printwheel. The PRPQ would then reformat the document filling in the skipped white space with the graphics from the other printwheel as appropriate. This process was repeated until all the required print wheels had a print pass. The Displaywriter solution was a specific solution to a specific printer and required specific code. DisplayWrite 2 and 3 provide IBM 5218 printer print support through the Class C print class. This logic will search the available printwheel list for the requested graphic in a method similar to the Displaywriter. The early DisplayWrite versions will attempt to make the best use of the mounted printwheel for a particular line; however, a typical document using cursor draw or scientific equations will still require many operator interventions to exchange printwheels. DisplayWrite 4 (DW4) provides IBM 5218 support through a Printer Function Table (PFT), which is very similar to the Printer Description Tables (PDT) of DW3 Class F print support. One of the differences is that a PDT would only print characters known to the IBM Graphics printer (PC Character Set 2), whe...