In computing and operating systems, a trap, also known as an exception or a fault, is typically a type of synchronous interrupt typically caused by an exceptional condition (e.g., breakpoint, division by zero, invalid memory access). A trap usually results in a switch to kernel mode, wherein the operating system performs some action before returning control to the originating process. A trap in a system process is more serious than a trap in a user process, and in some systems is fatal. In some usages, the term trap refers specifically to an interrupt intended to initiate a context switch to a monitor program or debugger.
Deriving from this original usage, trap is sometimes used for the mechanism of intercepting normal control flow in some domains.
In SNMP, a trap is a type of PDU used to report an alert or other asynchronous event about a managed subsystem.