4.2 - Role Of An Operating System Flashcards
What does the OS do?
Forms a bridge between the physical hardware of a computer and the user or application software
What is the APS?
Application Processing Software
Provides functions that a developer can call to interact with the OS
Let’s one piece of software communicate with another
What are the functions of an OS?
Memory management
Processor scheduling
Backing store management
Peripheral management of IO devices
How does memory management work?
PC allows many processes to be running at the same time
The OS allocates memory to each separate process the user is carrying out
If there is not enough memory the program may be swapped out of memory onto disk or “virtual memory” and reloaded when activated
What is processor scheduling?
The OS controls which programs can send data to the processor to be processed
Instructions from multiple operations are queued
What is multi-tasking?
When the processor executes small parts of each operation in turn so that programs appear to run simultaneously
What does the scheduler do?
It is the OS module responsible for ensuring that processor time is used as efficiently as possible
What are the 3 scheduling algorithms?
- round robin - each process in turn has use of the processor for a given time slice
- shortest job next
- priority system
What does the task manager do?
Windows task manager shows the processes that are currently running and the allocation of resources
What is backing store management?
OS keeps track of where all files are stored on hard disk or external drives and where spaces is free to be used if the user performs a save operation.
Files can be listed, moved, deleted, protected from unauthorised access
Keeps track of files split across disk sectors
Controls access permission to files
What is IO (input output) device management?
Communicates with I/O devices via the I/O controller, part of the CPU
Checks that a required output device is switched on and ready to receive data
Deals with processor ‘interrupts’
