Assessment improvements Flashcards
What is a device driver?
A device driver is a program that controls a piece of hardware, providing an interface between the device and OS.
What are three characteristics of virtual memory?
Memory contents are divided into pages
Pages not needed are moved to virtual memory - an area on a secondary storage device
When required, the pages are moved from virtual memory back into RAM.
What is an interrupt?
An interrupt is a signal to the processor indicating a device/process needs attention.
What happens when the CPU receives an interrupt?
If an interrupt is of lower or equal priority to the current process, the current process continues
If it is of higher priority, the CPU finishes its current FDE cycle before taking action
The contents of the CPU’s registers are copied into the stack in memory
The location of the appropriate ISR is loaded into the PC
When the ISR is complete, the previous contents are popped from the stack and loaded back into the registers
Why may first come, first served scheduling be inefficient?
Once a job starts, it prevents other jobs from being processed. A job using a slow resource wastes processor time
Why is scheduling necessary?
Scheduling is needed so that as many jobs as possible are able to be processed in the least possible time.
It ensures all jobs are processed fairly and makes efficient use of resources/processor time
