Systems Software Flashcards
What is paging
Programs split up into equal-sized pages which can be swapped between main memory and hard-disk as needed.
Operating System Functions
Memory management
Security (Firewall)
Input/Output management
Interrupt management
What is segmentation
Splitting up memory into varying size divisions which are representative of the structure of the program.
Describe virtual memory
Secondary storage is used as RAM when RAM is full, sections that are not in use are sent to virtual memory
Interrupts:
Stored in a priority queue in the interrupt register
Interrupt service routine:
At the end of an FDE cycle the interrupt register is checked, if needed the appropriate Interrupt Service Routine will be uploaded, and the contents of the special purpose registers are temporarily moved to a stack.
What is Scheduling
Making sure all programs have the right service time
Evaluate Round Robin
(equal time between them)
+ Easy to implement
- Some jobs take really long
Evaluate First come first served
+ Easy to implement
- Some jobs take too long
Evaluate Multilevel feedback queues
- Not easy to implement
Evaluate Shortest job first
- Calculating time remaining is hard
- Processor starvation if short jobs flood
Evaluate Shortest time remaining
- Calculating time remaining is hard
- Processor starvation if short jobs flood
All types of OS
Distributed: Across multiple devices
Embedded: Consumes less power
Multi-tasking: Uses time slicing to seeming switch between tasks quickly
Multi-user: In a supercomputer
Real Time: Used in time-critical systems: Performs a task in a guaranteed amount of time.
What does the BIOS do
POST – ensures all hardware is connected
Checks memory and processor are operational
Tests external devices
Loads OS.
What do Device Drivers do
Allows the OS to interact with hardware, as it communicates requests inputted by hardware
