A software-generated interrupt caused either by an error or a user request is known as what?

A software-generated interrupt caused by either an error or a user request is referred to as a "trap." This term specifically indicates an intentional or unintentional event that alters the control flow of a program, often leading to an exception handler or a system service that deals with the condition that caused the trap.

Traps can occur due to various reasons, including attempting to access invalid memory, dividing by zero, or invoking system calls that request services from the operating system. In these situations, the operating system can take the necessary actions to either handle the error, provide feedback, or fulfill the user request by transitioning control to the appropriate handler designed for that specific situation.

The other terms have different meanings in the context of operating systems. While an "interrupt" is a broader term that can encompass both hardware and software interruptions, it does not specifically refer to those generated by errors or requests. A "lost interrupt" refers to an interrupt signal that is missed or disregarded by the CPU, typically due to timing issues. A "system call" represents a request made by a program for a service provided by the operating system, but it is not a direct synonym for a trap.