operating system - Why is an interrupt caused at the END of an operation? -


i'm reading on device controllers , rather confused following point:

the device controller informs cpu has finished operation causing interrupt

to me, seems defy intuitive notion of interrupt is, ie "to stop continuous progress of (an activity or process)". shouldn't interrupt occur @ beginning or throughout controller's execution, , stop once controller finished?

for example, if send command on computer print document, i'm imagining there's message being sent printer pc signal end of execution, wouldn't think of interrupt. if i/o device has finished execution, shouldn't free more resources os?

see, interrupts reverse of thinking of!

the interrupts inform cpu operation has been completed! please removing process physical memory , thereby releasing resources!

the interrupts triggered @ beginning well,but,can imagine happen if interrupts have been hanging everytime withing process execution? won't cpu frustrated because of enormous calls everytime have been avoided following normal procedure!

it's rather efficient step cause interrupt @ end(and @ beginning too) because meanwhile cpu busy doing other task, becomes work of device controller cause interrupt inform cpu hey cpu, work has been done, please free resources , kill process!

where sad/in-efficient part here???


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