Browse Prior Art Database

Typewriter Display Having Double-Width Characters

IP.com Disclosure Number: IPCOM000039741D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Loiselle, JT: AUTHOR [+3]

Abstract

Double-width characters are shown on an all-points-addressable (APA) display of a typewriter or printer in exactly the same way that they are printed on a sheet of paper to provide a true relationship to the tabs and margin scale. To display a double-width character on an APA display, which is a cathode ray tube, the character code, which allows selection of the correct character font data, and the character attributes, which indicate whether the characters are to be displayed normal width or double width, are passed to a Display Control processor. If the character attributes indicate that the character is double width, the video RAM write display within the Display Control processor replicates the bits of each byte read from the character font so that two bytes are written to the video RAM for each byte of font data.

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Typewriter Display Having Double-Width Characters

Double-width characters are shown on an all-points-addressable (APA) display of a typewriter or printer in exactly the same way that they are printed on a sheet of paper to provide a true relationship to the tabs and margin scale. To display a double-width character on an APA display, which is a cathode ray tube, the character code, which allows selection of the correct character font data, and the character attributes, which indicate whether the characters are to be displayed normal width or double width, are passed to a Display Control processor. If the character attributes indicate that the character is double width, the video RAM write display within the Display Control processor replicates the bits of each byte read from the character font so that two bytes are written to the video RAM for each byte of font data. For example, if a byte of font data contains b'00110001', two bytes with the byte pattern b'00001111' and b'00000011' would be written to the video RAM to double the width of that portion of the character.

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