System Status Indicators
Original Publication Date: 1978-Mar-01
Included in the Prior Art Database: 2005-Feb-20
In a stored program computer, four explicit machine states and two explicit input/output (I/O) states are encoded into three console indicator lights, as illustrated in Fig. 1. The states have the following meaning: RUN -- Tasks are being processed. WAIT -- Tasks are not being processed, but task dispatcher has been enabled. Either all tasks have been completed, or all tasks are waiting for one or more I/O operations to complete. The system will go from WAIT to RUN when tasks are to be processed, due to I/O operations being completed, or due to additional tasks being initiated by the operator. MANUAL -- Tasks are not being processed, due to operator intervention. The task dispatcher is disabled, thus preventing any new I/O operations or other user functions from being initiated.