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Implementation of Field Inheritance

IP.com Disclosure Number: IPCOM000041847D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Beaven, PA: AUTHOR [+4]

Abstract

In an extended IBM 3270 data stream display, each character on the display is represented by a Character Code byte plus additional bytes. These additional bytes are known as Character Attributes (CAs) and contain display characteristics of the character (e.g., Font, Foreground and Background color, etc.). Not all of the Character Code positions represent valid characters. Certain positions are used for Field Attributes (FAs) and contain information that applies to all subsequent characters (until the next Field Attribute). The additional bytes associated with the Field Attribute are known as the Extended Field Attribute (EFA), and the display characteristics that are defined in them are used as default values for subsequent characters.

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Implementation of Field Inheritance

In an extended IBM 3270 data stream display, each character on the display is represented by a Character Code byte plus additional bytes. These additional bytes are known as Character Attributes (CAs) and contain display characteristics of the character (e.g., Font, Foreground and Background color, etc.). Not all of the Character Code positions represent valid characters. Certain positions are used for Field Attributes (FAs) and contain information that applies to all subsequent characters (until the next Field Attribute). The additional bytes associated with the Field Attribute are known as the Extended Field Attribute (EFA), and the display characteristics that are defined in them are used as default values for subsequent characters. The default values are used by subsequent characters when the value in the Character Attribute specifies default. This defaulting is known as Field Inheritance. In current displays the Character Codes, Character Attributes, Field Attributes and Extended Field Attributes are stored in a Display Buffer. The display logic reads this information from the Display Buffer and performs the inheritance on the Character Attribute before using it. This is shown in Fig. 1. This form of implementation has two disadvantages: 1. In order to avoid problems due to 'wrap around' of the Field Attribute when there are adjacent vertical partitions, it is necessary to have a 'margin' Field Attribute at the start of ea...