(1) A mechanism by which a process can be notified of, or affected by, an event occurring in the system. Examples of such events include hardware exceptions and specific actions by processes. The term signal is also used to refer to the event itself.
(2) In operating system operations, a method of inter-process communication that simulates software interrupts.
(3) In replication, an SQL statement that allows communication with the Capture program and the Q Capture program. A signal is inserted into the signal control table and received by the Capture program or the Q Capture program when the program reads the log entry for the signal insert.
(4) In UML modeling, model elements that specify one-way, asynchronous communications between active objects and that are independent of the classifiers that handle them.
(5) A condition that might or might not be reported during program execution. For example, a signal can represent erroneous arithmetic operations, such as division by zero.