An interrupt is a messagesignal from a device, such as the keyboard, to the CPU, telling it to immediately stop whatever it is currently doing and do something else. For example, the keyboard controller sends an interrupt when a key is pressed. To know whathow to docall on the kernel when a specific interrupt arise, the CPU has a table called the '''[[IDT]]''', which is a vector table setup by the OS, and stored in memory. There are 256 interrupt vectors on x86 CPUs, numbered from 0 to 255 which act as entry points into the kernel. The number of interrupt vectors or entry points supported by a CPU differs based on the CPU architecture.
There are generally three classes of interrupts on most platforms:
