Browse Prior Art Database

Method to Provide Concurrent Update of Multiple Physical Displays by Multiple Virtual Terminals

IP.com Disclosure Number: IPCOM000039426D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Geise, DM: AUTHOR

Abstract

Some Display Management Subsystems allow multiple virtual terminals to be created. Each virtual terminal uses one and only one physical display at a time; however, many virtual terminals may share the same physical display. Fig. 1 illustrates the case where "N" virtual terminals share one real display. To avoid update conflicts, the concept of "ACTIVE" virtual terminal was introduced. Only the "active" virtual terminal has the right to update the real display. All other virtual terminals must update their internal representation (Presentation Space) of the information that would have been displayed had they been the "ACTIVE" virtual terminal. This new method gives "non-active" virtual terminals the ability to update their associated real displays concurrent with the "active" virtual terminal. As shown in Fig.

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Method to Provide Concurrent Update of Multiple Physical Displays by Multiple Virtual Terminals

Some Display Management Subsystems allow multiple virtual terminals to be created. Each virtual terminal uses one and only one physical display at a time; however, many virtual terminals may share the same physical display. Fig. 1 illustrates the case where "N" virtual terminals share one real display. To avoid update conflicts, the concept of "ACTIVE" virtual terminal was introduced. Only the "active" virtual terminal has the right to update the real display.

All other virtual terminals must update their internal representation (Presentation Space) of the information that would have been displayed had they been the "ACTIVE" virtual terminal. This new method gives "non-active" virtual terminals the ability to update their associated real displays concurrent with the "active" virtual terminal. As shown in Fig. 2, either VT1 or VT3 could update real display 1 concurrent with VT4's (the active virtual terminal) updates of real display 2. These concurrent updates are accomplished with the following methodology:

(Image Omitted)

1. When a virtual terminal becomes "ACTIVE," it stores its

identification number (ID) in the "Last VT Active" field of a

data structure called the REAL SCREEN TABLE. This table is

shared by all virtual terminals in the system. Each entry in

the table describes the attributes of one of the real displays

that are attached to the system. Each such entry...