Abstract: A computer system receives a number of different dependent variable data sets, all varying with respect to a single independent variable such as time, and displays a plot of each data set on a different one of a set of graphs, all of the graphs having conforming and preferably identical, aligned scales of the independent variable. The identical scales for the common independent variable are preferably in precise vertical alignment, which allows the viewer to more easily see relationships in the changes of the dependent variable data sets as the independent variable changes.

Abstract: A computer has access to a number of data items available from at least one data source. The computer receives requests for the values of certain of these data items from a number of different clients which may be either devices external to the computer or application programs operating in a multitasking environment within the computer. As each request is received from a client, it is stored in a data item table. The computer replies to each client request in the data item table with a data item value available somewhere in the data item table. The computer updates older data item values held by the data item table by requesting those data item values from the data sources which provide them. The data item values supplied to clients are those from previously received data source replies if these replies are not too old.

Abstract: A display system provides a real time display on its display screen of the present and recent past operating history of an operating system. The operating system provides a signal to the display system in real time which encodes the current operating state of the operating system. For each operating state, a line is displayed in the display screen at a coordinate position which associates the line with the operating state. Each of these lines is coordinated with a time scale running along the screen which indicates the actual time intervals during which the various states existed.

Abstract: A display system for dynamically indicating the status of conditions of a physical system shows as background on a raster display unit, a sketch of the physical system with text indicating the status of the various conditions juxtaposed to the sketch. In the preferred embodiment, the text for each condition is placed adjacent the general area on the sketch to which the condition pertains. It is intended that this display system will be implemented on a general purpose computer system by executing software which converts the computer system into the display system.

Abstract: Apparatus and method for sensing the operating condition of a burner temperature as the indicating variable. When the operating status is stable, the flue temperature should be nearly identical to that when the system was known to be in proper condition. During a time when the system is known to be in proper operating condition, the flue temperature is recorded during stable operation for a number of different firing rates. When identical or similar firing rates occur at a later time and operation is stable, the operating flue temperature is compared with the current flue temperature, and if substantially different, an operation status signal is set to a state indicating this change in operating condition.