Bull Hn Information Systems, Inc.

Christopher R Bailey

Kin C Yu

James W Stonier

Daniel G Peters

John R Mandile

Steven D Lizotte

Teresa L Wu

Charles T Mighill

A hybrid system environment includes a proprietary operating system and processing unit and a non-proprietary operating system (UNIX based) and processing unit. The systems tightly couple to a system bus in common with a main memory and a number of multiline communications controllers and communicate through a common area of main memory. The UNIX terminal connections to such controllers are virtual connections applied by a virtual terminal driver through the system proprietary communications software components. These components include a server, a network terminal driver (NTD) and a number of multiplexer driver modules. A multiplexer physical terminal driver is included in the UNIX-based operating system and a switching mechanism is incorporated into the virtual terminal driver for enabling switching to such physical terminal driver when a user switches via a switch command to the UNIX-based operating system. The server module upon being invoked upon such switching operates to establish a direct communications path between an application running under the UNIX-based operating system and the controller communications line paths through the multiplexer driver module and logically disconnects the virtual communications line path from the NTD module to the multiplexer driver module thereby improving system efficiency and terminal connectivity.

System for switching between two different operating systems by invoking

In a data processing system having a plurality of remote terminals, possibly of several kinds, connected by a plurality of communications media, also possibly of several kinds, from which terminals users may run a plurality of application programs in the central processing unit (CPU) of the data processing system, the CPU is provided with a network terminal driver for regulating transmissions between the various application programs and the various types of terminals over the various types of communications media. Means are provided for specifying the characteristics of the various types of application programs, terminals, and communications media, and the network terminal drive is responsive to those means.

Network terminal driver communications subsystem

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Hollis, NH, United States of America

Christopher R Bailey