Abstract: A computer system has a universal channel and control unit to interface, with a minimum complexity, to a plurality of different I/O adapters such as a Token Ring adapter or an Ethernet adapter. The system comprises a main processor with main memory, an I/O processor coupled to the main processor by a bus, and a channel program which runs on the I/O processor. The channel program accesses the processor and main memory. The channel program and main processor communicate with a first I/O program protocol. A control unit program also runs on the I/O processor and interfaces the channel program to a plurality of different I/O adapters with a second relatively simple, universal I/O program protocol. Each of the I/O adapters also has a different I/O program protocol than the other I/O adapters and the first I/O protocol, for communication with their respective device.

Abstract: A method of transforming a first editable form of a document prepared by an interactive text processing system into a second and incompatible editable form for use in another interactive or batch text processing system through the use of a transform mechanism is described. A significant step of this method requires the identification of a limited number of key state variables, whose values collectively identify the necessary state information for transforming the first document form to the second. After the key state variables have been identified, the actual number of combinations thereof is determined. For each first document form input item encountered by the transform mechanism, and for each combination of key state variables in which that input item can be encountered, one or more output items for the second document form is explicitly defined as the transform thereof. In addition, the state of the transform mechanism after each such transform has occurred, must also be specified.