Browse Prior Art Database

Combinational Character Generation

IP.com Disclosure Number: IPCOM000074740D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Mitchell, JO: AUTHOR [+2]

Abstract

Combinational-characters are characters that have two discrete symbols to make up a character. The prime examples are the accented characters used in some European languages. In the drawing, two accented characters "U" and "A" with the accents above the characters are shown. Additional examples of combinational-characters are the use of a cursor to point to a character, as in the "D" with the cursor shown below the "D". A last example is characters formed by overlaying two symbols, such as the "0" with the overlay "/" shown.

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Combinational Character Generation

Combinational-characters are characters that have two discrete symbols to make up a character. The prime examples are the accented characters used in some European languages. In the drawing, two accented characters "U" and "A" with the accents above the characters are shown. Additional examples of combinational-characters are the use of a cursor to point to a character, as in the "D" with the cursor shown below the "D". A last example is characters formed by overlaying two symbols, such as the "0" with the overlay "/" shown.

The apparatus to be described will generate these combinational-characters on the face of a cathode-ray tube. The characters or symbols are divided into two groups -- indexed characters and nonindexed characters. The primary alphabetic characters, such as D, U, A, and 0, are all indexed characters. The nonindexed characters are the cursor, the accent marks, and the slash. In operation, a series of indexed characters will be printed successively automatically by the system. To form a combinational-character, the index character is followed by a nonindexed character. Nonindex meaning that the deflection yoke of the cathode-ray tube is not indexed to the next position. Therefore, nonindexed characters will appear at the same position as (i.e., overlay) the previous index character in the character or text stream.

In operation, the text stream to be displayed is stored in the regeneration buffer 10. The text stream is stored in the form of addresses which are used to call character display data from a read-only storage 12. When the start regeneration signal is received at the regeneration buffer address 14, the first two character addresses are passed from the regeneration buffer 10 to the initial address register 16. The first address is passed on to the read-only storage address register 18 and controls access to the character display data in storage
12.

Raster controls 20 control the deflection of the cathode-ray beam to different areas of the screen of the tube. Display cycle controls 22 energize the raster controls 20 first and the read-only function of storage device 12 second, during each display cycle for a character. When the cathode-ray beam has been deflected to the correct position, display controls 22 enable the read-only storage 12 to read the addressed character display data to the character display buffer
24. The character display word in buffer 24 contains unblank data and writing deflection data to cause the cathode-ray tube to generate the character on the cathode-ray tube screen. The position of the character on the screen is controlled by the deflection yoke 21.

Usually, more than one character display word from read-only storage is required to generate a whole character on the screen of the tube. To address the next word of the same character display, a portion of the previous word is used as the address for the next word. This ad...