Explain briefly the working of semaphore with example ?, Operating System

Assignment Help:

Explain briefly the working of semaphore with example ?

The E.W. Dijkstra (1965) abstracted the key idea of mutual exclusion in his concepts of semaphores.

Definition
A semaphore is a confined variable whose value is able to be accessed and altered only by the operations P and V and initialization operation called as 'Semaphoiinitislize'.

Binary Semaphores is able to assume only the value 0 or the value 1 counting semaphores as well called general semaphores can assume only nonnegative values.

The P or sleep or wait or down operation on semaphores S written as P(S) or wait (S) operates as follows:

P(S):  IF  S > 0
                THEN S:= S-1
                 ELSE   (wait on S)

The V or wakeup or signal or up operation on semaphore S written as V(S) or signal (S) operates as follows:

V(S)   IF (one or more process is waiting on S)
                THEN (let one of these processes proceeds)
                ELSE   S: = S +1

Operations P and V are complete as indivisible, single, atomic action. It is guaranteed that formerly a semaphore operation has stared, no other process are able to access the semaphore until operation has completed. The Mutual exclusion on the semaphore S is enforced within P(S) and V(S).

If several processes attempt a P(S) concurrently only process will be allowed to proceed. The other processes will be set aside waiting however the implementation of P and V guarantees that processes will not suffer indefinite postponement.

Semaphores resolve the lost-wakeup problem.


Related Discussions:- Explain briefly the working of semaphore with example ?

Explain medium term scheduling, Medium term scheduling This is componen...

Medium term scheduling This is component of the swapping function. Usually the swapping in decision is based on the need to manage the degree of multiprogramming. At a system t

Explain types of file allocation-contiguous allocation, Contiguous allocati...

Contiguous allocation: Every file will be allocated contiguous space in the memory. Allow the block size be 1K If a 50K files desires to be allocated space after t

Tree directory structure, please help us to write a code in c for tree dire...

please help us to write a code in c for tree directory structures.

Performance of job scheduling strategies, Performance of Job Scheduling  St...

Performance of Job Scheduling  Strategies In this project you will investigate the performance of Job Scheduling strategies, Memory Allocation strategies and a CPU Scheduling s

CPU sheduling, categorize the CPU scheduling algorithms and among them expl...

categorize the CPU scheduling algorithms and among them explain the non-preemptive algorithms..

Write a note on multithreading, Write a note on multithreading. Multith...

Write a note on multithreading. Multithreading is the capability of an operating system to execute different parts of a program called as threads, at the same time. The program

Explain deadlock prevention, Deadlock Prevention Prevention is the name...

Deadlock Prevention Prevention is the name given to method that guarantee that deadlocks can never happen for the reason that the way the system is structured. Since 4 conditio

Illustrate different ways that threads could be implemented, Q. Multithread...

Q. Multithreading is a commonly utilized programming technique. Illustrate three different ways that threads could be implemented. Describe how these ways compare to the Linux clon

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd