Browse Prior Art Database

Erasing Characters on a Cathode Ray Tube Screen

IP.com Disclosure Number: IPCOM000039459D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hays, DE: AUTHOR

Abstract

Characters on a cathode ray tube (CRT) screen are erased by rewriting the message text in the screen's background color so that the message text does not appear on the CRT screen. To write text to a CRT screen of a personal computer (PC), the text and character attributes, such as underlining, highlighting, and the like, must be written to a special memory area of the PC with this special memory area being scanned by the PC hardware to create the screen display. When a text message/annunciator is to be erased from the CRT screen, the message text can be rewritten by specifying the background color, such as black, in a monochrome CRT screen. Thus, the same code that displayed the text, except for one statement to change the color, can be used to erase it. Accordingly, the attributes of the text need not be modified.

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Erasing Characters on a Cathode Ray Tube Screen

Characters on a cathode ray tube (CRT) screen are erased by rewriting the message text in the screen's background color so that the message text does not appear on the CRT screen. To write text to a CRT screen of a personal computer (PC), the text and character attributes, such as underlining, highlighting, and the like, must be written to a special memory area of the PC with this special memory area being scanned by the PC hardware to create the screen display. When a text message/annunciator is to be erased from the CRT screen, the message text can be rewritten by specifying the background color, such as black, in a monochrome CRT screen. Thus, the same code that displayed the text, except for one statement to change the color, can be used to erase it. Accordingly, the attributes of the text need not be modified. This avoids the need for a different code for writing a message on the screen than erasing it as occurs with the normal procedure of clearing all memory locations having the text message/annunciator to be erased from the CRT screen.

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