Browse Prior Art Database

Method of Eliminating Transmission of Excess Display Data

IP.com Disclosure Number: IPCOM000036302D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Callaway, JR: AUTHOR [+3]

Abstract

A method of determining when queued data becomes expendable is disclosed. An application allowing remote control telephone access to a desktop (host) computer must mirror the host's display screen. A "display monitor" periodically makes a copy of a host's display buffer and compares it with the display screen of a remote computer. The data is analyzed to find changes that have occurred. The data that has changed is enqueued to be sent to the remote computer as a display update.

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Method of Eliminating Transmission of Excess Display Data

A method of determining when queued data becomes expendable is disclosed. An application allowing remote control telephone access to a desktop (host) computer must mirror the host's display screen. A "display monitor" periodically makes a copy of a host's display buffer and compares it with the display screen of a remote computer. The data is analyzed to find changes that have occurred. The data that has changed is enqueued to be sent to the remote computer as a display update.

In a situation with major changes occurring on the host display screen, a great deal of data may be queued to be sent to the remote system. In that case it may take quite some time for the remote display screen to catch up with the current state of the host display. To avoid this problem, a frequent check of the display buffer is made to determine if a major change has occurred. If there has been a major change to the screen and there is a lot of display data queued, the queue is purged and the current screen is sent to the remote.

The performance of an application such as the one described is tied directly to the transmission rate on the telephone line. If the systems are running with modems operating at 1200 bits per second, about 120 characters may be transmitted in one second. This means that it may take approximately seven seconds to transmit half of a 25-line display screen to the remote system, which is very slow compared to normal PC performance.

If a user is familiar with an application that he is running remotely, he may "type ahead"; that is, he may press keys without waiting to see the display respond to the previous keys. For example, the user might page down rapidly through a document that is being edited. Another example would be if a user rapidly selects items from a sequence of menus with which the user is so familiar that it has become unnecessary to see the menus in order to know which keys to select. In either of these examples, the amount of data being displayed in rapid succession will cause a large time lag between the host display changes and the reception and display of the same data on...