Browse Prior Art Database

Multiple-Level Screen Buffer Management Technique

IP.com Disclosure Number: IPCOM000040723D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Batalden, GD: AUTHOR [+4]

Abstract

This technique allows an unlimited number of fields on an async terminal device. This is done without requiring an overly large amount of storage which contains information describing each field. In this context, a field is an area of the display used for a single input or output data item. A field description includes the position, size, and other attributes such as reverse video, or numeric only. In addition to allowing a variable number of fields, this technique also improves the response time seen by a user of a terminal connected by async. Very simplistically, the technique involves maintaining in the processor's main memory a "picture" of what has been displayed on the terminal.

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Multiple-Level Screen Buffer Management Technique

This technique allows an unlimited number of fields on an async terminal device. This is done without requiring an overly large amount of storage which contains information describing each field. In this context, a field is an area of the display used for a single input or output data item. A field description includes the position, size, and other attributes such as reverse video, or numeric only. In addition to allowing a variable number of fields, this technique also improves the response time seen by a user of a terminal connected by async. Very simplistically, the technique involves maintaining in the processor's main memory a "picture" of what has been displayed on the terminal. This "picture" can then be used to both reduce the amount of data transmitted to the device and also determine the fields and attributes of the display. Data transmission over an async line is generally much slower than some other media, such as twinax or LAN (Local Area Network). Therefore, one problem operating a terminal via async is performance. It is possible to improve the performance of an async attached terminal by minimizing the data which must be transmitted. To do this a "picture" of the data currently displayed on a terminal is maintained in processor memory. When additional data is displayed, the new data can be compared with what is currently displayed. Then, only changes from the previous display are transmitted to the terminal. For many updates, this reduces data traffic by an order of magnitude or more. With relatively slow async lines, this is an obvious improvement in the performance seen by a user. To maintain a "picture" of what has been displayed, the processor must record both the characters displayed and some descriptive information about each character. This i...