1.2.1 Flashcards
What is an operating system?
A collection of programs which work together to provide an interface between the user and computer
What are the functions of an OS?
- memory management
- resource management
- provide security
- file management
- input/output device management
- utility software
- user interface
What is memory manageme?
The act of fairly sharing computer memory between multiple programs and applications
What are the 2 types of memory management?
- paging
- segmentation
What is paging?
Where memory is split into divisions of equal size
What is segmentation?
Where memory is split into logical divisions of variable size
What is virtual memory?
Where a section of the hard drive acts as RAM and pages are swapped between RAM and the hard disk
What is disk thrashing?
When the computer freezes as a result of pages being swapped too frequently
What is an interrupt?
A signal from a software/hardware to indicate to the processor that a process needs attention
What is the interrupt service routine?
- the interrupt register is checked
- if a high priority interrupt is present, contents of registers are pushed onto a stack
- the interrupt is serviced
- the stack is popped back into the registers
What is round-robin?
All processes queue up for a time slice. If the process doesn’t complete in this time, it’s sent to the back of the queue
What are the drawbacks of round robin scheduling?
- doesn’t consider priority
- longer jobs take much longer to complete
What is first come first serve?
Processes are processed in the order in which they arrive until completion?
What are the drawbacks of first come first serve scheduling?
Doesn’t consider priority
What is a multi level feedback queue?
Multiple queues are used in order or their priority
What is shortest job first?
The shortest job in the queue is run until completion
What is shortest remaining time?
The job with the shortest time remaining until completion is run next
What is an embedded OS?
Can perform a small range of specific tasks
What is a distributed OS?
Runs across multiple devices allowing the load to be spread over multiple processors
What is a multi-tasking OS?
Allows multiple programs and instructions to be run simultaneously
What is a multi user OS?
Allows multiple users to use the same computer
What is a real time OS?
The processes run within a guaranteed time frame
What is the BIOS?
- the first program run when a computer is switched on
What does the BIOS do?
- check all components working correctly
- checks clock/ memory/ processor working
- loads OS into memory
What is a device driver?
A piece of software that allows the OS to interact with hardware devices
What is a virtual machine?
A software implementation of a computer system which allows intermediate code to run
What is intermediate code?
Halfway between machine and object code and is not processor specific
