Explain and bring out the differences between interrupt and exception.

The UNIX system allows devices such as I/O peripherals or the system clock to interrupt the CPU asynchronously. On receipt of the interrupt, the kernel saves its current, determines the cause of the interrupt, and services the interrupt. 

The hardware usually prioritizes devices according to the order that interrupts should be handled. When the kernel services an interrupt, it blocks out lower priority interrupts but services higher priority interrupts.

An exception condition refers to unexpected events caused by a process, such a addressing illegal memory, executing privileged instructions, dividing by zero, and so on. They are distinct from interrupts, which are caused by events that are external to a process. 

Exceptions happen "in the middle" of the execution of an instruction, and the system attempts to restart the instruction after handling the exception; interrupts are considered to happen between the execution of two instructions, and the system continues with the next instruction after servicing the interrupt. The UNIX system uses one mechanism to handle interrupts and exception conditions.

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