Windows Internals, Fifth Edition

Trap Dispatching

Interrupts and exceptions are operating system conditions that divert the processor to code outside the normal flow of control. Either hardware or software can detect them. The term trap refers to a processor’s mechanism for capturing an executing thread when an exception or an interrupt occurs and transferring control to a fixed location in the operating system. In Windows, the processor transfers control to a trap handler, a function specific to a particular interrupt or exception. Figure 3-1 illustrates some of the conditions that activate trap handlers.

The kernel distinguishes between interrupts and exceptions in the following way. An interrupt is an asynchronous event (one that can occur at any time) that is unrelated to ...