Systems software Flashcards
what do operating systems provide
an interface between the user and computer
what do operating systems enable
- communication with the computer
- preform low-level tasks involving memory and resource management
what are operating systems essential for (7 things)
- memory management
- resource management
- file management
- input/output management
- utility software
- interrupt management
- user interface
paging
splits memory into equal-sized pages that can be swapped between main memory and the hard disk
segmentation
splits memory into logical divisions
virtual memory
uses a section of the hard drive as RAM when main memory is insufficient
with unused program sections moved to virtual memory through paging
how does an operating system deal with interrupts
- (Interrupt Service Routines (ISR) are loaded into RAM to respond to interrupts) - before
- interrupts checked for at the start/end of each FDE cycle
- if the interrupt is lower priority than the current process, then the current process will continue
- interrupt pushes the current register values into a stack
- interrupt is dealt with
- previous register values are restored from stack
types of scheduling algorithms (5)
- round-robin
- first come first served
- multi-level feedback queues
- shortest job first
- shortest time remaining
round-robin
allocates equal time slices to jobs
potentially leading to longer job completion times
does not consider job priority
shortest remaining time
orders jobs by time left for completion
risking processor starvation for longer jobs if short jobs are added
multi-level feedback queues
use multiple queues ordered by priority
challenging to implement
types of operating systems (5)
- distributed
- embedded
- multi-tasking
- multi-user
- real-time
