What is a Program Interrupt and its types?

Program interrupt refers to the transfer of program control from a currently running program to another service program as a result of an external or internal generated request. Control returns to the original program after the service program is executed.

After a program has been interrupted and the service routine been executed, the CPU must return to exactly the same state that it was when the interrupt occurred.

Types of Interrupts

External interrupts

• External interrupts come from input-output (I/O) devices, from a timing device, from a circuit monitoring the power supply, or from any other external source.
• External interrupts are asynchronous. External interrupts depends on external conditions that are independent of the program being executed at that time.

Internal interrupts

• Internal interrupts arise from illegal or erroneous use of an instruction or data. Internal interrupts are also called traps.
• Internal interrupts are synchronous with the program if the program is return, the internal interrupts will occur in the same place each time.

Software interrupts

• A software interrupt is a special call instruction that behaves like an interrupt rather than a subroutine call. It can be used by the programmer to initiate an interrupt procedure at any desired point in the program.

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