Operating System Flashcards
Purpose of operating system?
To provide interface between user and hardware
Multitasking
When you have more than one program open and running at the same rime
How does multitasking work
The processor allocates a small amount of time to each process and cycles between them
As this happens so quickly it appears as if multiple programs are executing simultaneously
User management
Allows multiple users to log onto the same computer
How does user management work
Operating system will retain settings for each user
Each user may have different access rights to files and programs
Features of user management
WIMP- windows, icons, menus, pointers
Visual
Interactive
Intuitive
Optimised for mouse and touch gesture input
Paging features
Fixed sizes
Physical divisions
Made to fit sections of memory
Programs are split up to fit into a given number of pages
Paging takes no account of how it splits the program, only that it splits it into fixed page sizes
Could separate instructions inside a looping condition so they are in different pages- not efficient
It would be better to keep those instructions together in memory
Segments features
Different sizes
Logical divisions
Complete sections of programs
Virtual memory
When programs and data are fetched and executed they are stored in RAM, there is more room available on the hard disk
If physical memory is running low, virtual memory must be used
If more time is spent moving pages/ segments from memory to the disk than processing instructions the computer will be slow
Virtual memory steps
1.Transfer instruction not being used into space on hard disk (virtual memory)
2.When instruction is needed again it will be transferred back into RAM
this gives the impression that the computer has more memory than it actually has
Interrupt
A way to signal to the processor that they require attention
Types of operating system
Multitasking
Multiuser
Embedded
Real time
Distrubuted
Multitasking operating system
In single processor systems, each active program is scheduled to recieve a t
