Abstract: 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.

Abstract: 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.