Operating Systems Flashcards
what is the purpose of operating systems
provides an interface between the user and the computer
what is file management
a function provided by the OS which allows the user to create, organise and rename files
what is memory management
a function provided by the OS which allocates and tracks resources to ensure efficient use of memory
what is input/output management
involves controlling the exchange of data between the computer and external hardware.
how does multitasking work
works by allocating processing time to each program, this happens in a cycle.
this creates an illusion of simultaneous operation
what is paging
when memory is divided into fixed sizes and programs are split up to fit these pages
what is segmentation
when memory is split up into different sizes (logical divisions)
what are the simmilarities of paging and segmentation
both allow programs to run on insufficient memory
what are the differences between paging and segmentation
pages are fixed sizes
segments are logical
how does an interrupt happen relating to FDE cycles
1.complete the current FDE cycle
2.save the registers to memory
3.determine the interrupt service
4.service the interrupt
5.restore the register values
6.continue the original process
what is a device driver
software that tell the operating system how to communicate with a device
how do driver routines work
- when a program requests to interact with a hardware device - it calls a routine within the driver software of that device
- the routine causes the hardware to perform a specific task
What bus is used for devices to communicate with the processor?
control bus
what are the different types of OS
multi tasking OS
multi user OS
Distributed OS
Embedded OS
real time OS
what is a distributed OS
where multiple computers work on a single task
the distributed OS coordinates the communication between nodes
what is an interrupt
a signal to the processor indicating a device or process needs attention
what is polling
where the CPU asks each process if an interrupt is needed
what are the steps to handling interrupts
1)the processor completes the current FDE cycle
2) the interrupt flag is checked to see if any interrupts have been raised(if so the priority is checked)
3)the higher priority tasks are executed first
4) the other interrupt tasks are then loaded from the stack to all the processors to be executed
how are the non interupt tasks loaded to a stack
and what happens to the interrupts
- the contents of registers are pushedto a stack
the address - the addess of the ISR is loaded into the PC(register)
- the ISR is executed
what is an ISR
a program that is designed to respond to an interrupt’s request
what is the purpose of a schedulling algorithm
to decide how processor time is split between processes
what is the difference between pre-emptive and non pre-emptive
pre emptive = a process can be replaced with a higher priority task
non pre emptive = once a job is started it is left alone until finished
what data structure is associated to scedulling
QUEUE (FIFO)
what does BIOS stand for
basic input output system
what are the tasks peformed by the BIOS
keeping track of the system time
testing the hadware that is connected as te computer boots
how does an operating system get the device driver of a mouse
the device drvier of the mouse is automatically downloaded by the
OS once the mouse is plugged in
what are the different jobs performed by the control bus
interrupts
clock signals
read/write signals
what is a virtual machine
a program that has the same functionality as a physical machine
what is a hypervisor
a program used to run and manage one o more virtual machine on a computer
what are the advantages of virtual machines
allows developers to test software developed for multiple platforms
can be used to test dangerrous code like viruses
what is system software
software that controls the hadware
what is utility software
software that perfporms a specific task that is usually related to the up keep of the system
what is the difference between specific and generic software
generic can be used for masny different tasks
specific is only used for specific tasks (usually takes lots of skill)
what is the purpose of disk defragmenters
helps to combine the different parts of the file together in contiguous space
