Abstract: Higher functions terminals and lower function terminals, as well as dual mode terminals that are selectively operated at either functional level, are simultaneously supported on a common control unit interface in an information handling system. Communications with single mode terminals are directed to a buffer portion having a predetermined base address. Each dual mode terminal contains a buffer that is partitioned into respective portions used for communications at different function levels. Communications at a lower functional level are conducted through the buffer portion containing the base address while communications at a higher functional level are redirected to a buffer portion containing shifted addresses. The control unit includes means for determining the suitable level of terminal function and adjusting the addressing of the terminal buffer accordingly.

Abstract: A method and apparatus for handling system service requests such as disk change requests in a system containing a primary processor and at least one secondary processor, each of which has one or more processes running thereon. Requests originating from processes running on the primary processor are added directly to a primary queue and the corresponding processes suspended pending the completion of the requested system service, at which time the processes are resumed and the requests are purged from the primary queue. Each secondary processor manages a secondary queue of system service requests originating from processes running on that processor, which are suspended while the requests remain on the secondary queue. When a request is added to an empty secondary queue, a process on the secondary processor issues its own request to the primary processor, which is added to the primary queue, and suspends execution while awaiting a response from the primary processor.

Abstract: In a computer terminal system, a communications buffer is provided in a remote device to receive and transmit data and control information from and to the remote controller via the transmission link connecting the two. The controller owns the buffer and places data at any point in the buffer and places data at any point in the buffer and tells the device to process it. The controller may write the data to another point in the buffer allowing full overlap.The controller can read data from the buffer or write data to the buffer while the device is processing. The controller is able to manage the use of the device buffer in accordance with the specific environment in which the controller is operating.