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Support of Application Unique Character Sets

IP.com Disclosure Number: IPCOM000062408D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Baker, DC: AUTHOR [+4]

Abstract

By detecting that a Unique Character Set is in effect, character codes can be sent to a Unique Translator for preprocessing into a stream of character codes that simulates the lower function addressability of other character sets to provide the required interface to Virtual Device Driver for the installed display. Additionally, by keeping two unique character sets to display symbol mappings in each virtual terminal, each application can uniquely specify two unique character sets, in addition to the predefined ones, thereby simplifying porting applications that make use of unique character sets. A Display Device Drive requires two pieces of information in order to select one of an array of 1024 symbols for screen display: an 8-bit character code and a 32-bit base.

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Support of Application Unique Character Sets

By detecting that a Unique Character Set is in effect, character codes can be sent to a Unique Translator for preprocessing into a stream of character codes that simulates the lower function addressability of other character sets to provide the required interface to Virtual Device Driver for the installed display. Additionally, by keeping two unique character sets to display symbol mappings in each virtual terminal, each application can uniquely specify two unique character sets, in addition to the predefined ones, thereby simplifying porting applications that make use of unique character sets. A Display Device Drive requires two pieces of information in order to select one of an array of 1024 symbols for screen display: an 8-bit character code and a 32-bit base. The driver uses the base as a starting point or offset for a 256-character set indexed by the character code. This allows for efficient use of the 8-bit codes to access all display symbols. However, the Unique Sets, a special sort of character set, are arrays of full 10-bit display symbols, addressing the entire range of 1024 symbols, instead of the smaller 256 sets. Those symbols contained in the Unique Sets actually would need no processing by the Device Driver before display, but because it is expecting data in a less processed state, the Unique Translator must simulate the less powerful addressing ability of the other standard character sets and turn a display symbol into a base and a character code. The Unique Translator extracts the display symbol out of the Unique character set and reads the 8 least significant bits to determine a character code. The two most significant bits are used to locate the display symbol within the bounds of a standard character set overlay on the display symbol array, thus producing the base expected by the Device Driver. However, because of the larger addressing range of the Unique Sets, the codes of a series of characters cannot be expected to remain within one of the predetermined standard character sets but, rather, can be found among various sets. It is desirable, however, for the sake of processin...