Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
33 Cards in this Set
- Front
- Back
|
Interrupt
|
A signal sent to the processor from an external entity asking that is pauses the current job and executes a job of a higher priority
|
|
|
4 categories of interrupt
|
I/O, Program, Hardware, Timer
|
|
|
Type of I/O interrupt
|
printer out of paper, printer out of ink, buffer empty
|
|
|
Type of program interrupt
|
divide by zero
|
|
|
Type of hardware interrupt
|
imminent power failure
|
|
|
Type of timer interrupt
|
Time slice system eg. in a round robin
|
|
|
Data structure that's allows a job to resumed once an interrupt has been serviced
|
Stack
|
|
|
Data structure that interrupts must wait in until they are ready to be serviced
|
queue
|
|
|
The 3 states a job can be after it has been sent to the processor
|
ready, running blocked
|
|
|
Program that decides what state each of the jobs should be in and in what order they should be processed
|
Scheduler
|
|
|
3 different parts of the scheduler
|
low level, medium level, high level
|
|
|
Pre-emptive scheduler can...
|
stop a running job and make way for another job
|
|
|
Non pre-emptive scheduler can...
|
can place a job in the running state but cannot force it out
|
|
|
Name 5 key scheduling algorithms
|
First in- first served
Round Robin Shortest Job First Shortest Remaining Time Multi Level Feedback Queue |
|
|
A safety critical system would need a scheduling algorithm based on...
|
priorities
|
|
|
Which scheduling algorithm favours short jobs the most
|
Shortest remaining time (it can move jobs out of the running state if a shorter one comes along).
|
|
|
What occurs at the end of a time slice
|
A timer interrupt
|
|
|
2 reasons a job will leave the running state in any algorithm
|
The job has been completed
The job has been blocked |
|
|
Two methods of partitioning memory
|
Paging and segmentation
|
|
|
Paging divides pages along ............... lines
|
physical
|
|
|
Segmentation divides segments along .............. lines
|
logical
|
|
|
Partitioning that divides memory into equal sized sections
|
paging
|
|
|
Partitioning that divides memory into different sized sections
|
segmentation
|
|
|
Similarities of paging and segmentation
|
Both involve partitioning memory
Segments and pages are stored on the backing store Segments and pages are assigned to memory when needed Allow programs to run even with insufficient memory |
|
|
Differences between paging and segmentation
|
Segments are different sizes but pages are of a fixed size
Segments are based on logical divisions whilst pages are physical divisions Segments are complete parts of programs, pages are designed to fit in sections of memory |
|
|
Disk thrashing
|
If there is a high rate of disk access more time is spent on swapping pages than processing them. A 'lag' in response time is felt.
|
|
|
Spooling
|
Spooling is where data is placed in a temporary storage area for another program/device to process.
The location reference of the job is stored in a spool queue. Jobs can be arranged in the spool queue based on priorities It avoids a speed mismatch caused by most devices e.g printer being much slower to read information than the processor can send it |
|
|
Purpose of boot file
|
stores personal settings
|
|
|
What is the boot file executed?
|
When the PC is switched on after the POST (Power on self test)
|
|
|
What is the File Allocation Table
|
This is like a map of where all parts of a file are stored in the hard disk.
It stores pointers to where different parts of files are stored It will signify when you have come to the end of the file |
|
|
State 5 things the FAT / File Directory stores
|
File names
Access rights start cluster of the file free space |
|
|
When is the FAT edited?
|
When a file is saved or deleted
|
|
|
When is the FAT accessed
|
Every time a file is opened
|
