38241635
Description
| Question | Answer |
| Generally, what is an Interrupt and the Two Main Types? | > Signal from a piece of software, hardware, or internal clock to the CPU > Efficiently tells the computer that a job needs to be completed > Allows for multi-tasking to take place > Software and Hardware interrupts |
| What is a Software Interrupt? | > Interrupts from a piece of software that needs to terminate or request services from the OS to continue running > For example, opening a file has to request read access |
| What is a Hardware Interrupt? | > Interrupts from a piece of hardware that occurs when an I/O operation completes, or encounters an error > For example, when a printer runs out of paper, the CPU must display that error to the user, and stop any more files from being sent |
| What is an Alternative to Interrupts? | > Polling > CPU polls (asks) every piece of software and hardware if anything needs doing every cycle > Very inefficient |
| What is an Interrupt Service Routine (ISR)? | > Set of instructions that needs to be completed as part of the interrupt (i.e., the reason why the CPU was interrupted in the first place) > The CPU returns to the previous instructions once the ISR is completed |
| How is an ISR Executed? | > Interrupt arrives at the CPU with a flag indicating its priority > The priority is checked at the end of each fetch, decode, execute cycle > If the interrupt's priority is higher than the current set of instructions, all registers are pushed to the system stack, and the ISR begins to be executed |
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