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Authors:
Linda Null ,julia Lobur
Chapter:
Marie An Introduction To A Simple Computer
Exercise:
Review Of Essential Terms And Concepts
Question:22 | ISBN:9780763704445 | Edition: 3

Question

22. Describe how an interrupt works and name four different types.

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Answer

An interrupt is a signal from a device attached to a computer or from a program within the computer that requires the operating system to stop and figure out what to do next.

Interrupt systems are nothing but while the CPU can process the programs if the CPU needs any IO operation. Then, it is sent to the queue and it does the CPU process. Later on Input/output (I/O) operation is ready.

The I/O devices interrupt the data which is available and does the remaining process; like that interrupts are useful. If interrupts are not present, the CPU needs to be in idle state for some time, until the IO operation needs to complete. So, to avoid the CPU waiting time interrupts are coming into picture.

Processor handle interrupts

Whenever an interrupt occurs, it causes the CPU to stop executing the current program. Then, comes the control to interrupt handler or interrupt service routine.

These are the steps in which ISR handles interrupts. These are as follows −

Step 1 − When an interrupt occurs let assume processor is executing i'th instruction and program counter will point to the next instruction (i+1)th.

Step 2 − When an interrupt occurs the program value is stored on the process stack and the program counter is loaded with the address of interrupt service routine.

Step 3 − Once the interrupt service routine is completed the address on the process stack is popped and placed back in the program counter.

Step 4 − Now it executes the resume for (i+1)th line.

The four diferent types of Interrupts are :

  • Maskable Interrupt − The hardware interrupts that can be delayed when a highest priority interrupt has occurred to the processor.

  • Non Maskable Interrupt − The hardware that cannot be delayed and immediately be serviced by the processor.

  • Normal Interrupts − The interrupts that are caused by the software instructions are called software instructions.

  • Exception − Exception is nothing but an unplanned interruption while executing a program. For example − while executing a program if we got a value that is divided by zero is called an exception.

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