A deadlock happens in operating system when two or more processes need some resource to complete their execution that is held by the other process.A deadlock occurs if the four Coffman conditions hold true. But these conditions are not mutually exclusive. They are given as follows −Mutual ExclusionThere should be a resource that can only be held by one process at a time. In the diagram below, there is a single instance of Resource 1 and it is held by Process 1 only.Hold and WaitA process can hold multiple resources and still request more resources from other processes which are ... Read More

Cooperating processes are those that can affect or are affected by other processes running on the system. Cooperating processes may share data with each other.Reasons for needing cooperating processesThere may be many reasons for the requirement of cooperating processes. Some of these are given as follows −ModularityModularity involves dividing complicated tasks into smaller subtasks. These subtasks can completed by different cooperating processes. This leads to faster and more efficient completion of the required tasks.Information SharingSharing of information between multiple processes can be accomplished using cooperating processes. This may include access to the same files. A mechanism is required so that ... Read More

Process Scheduling handles the selection of a process for the processor on the basis of a scheduling algorithm and also the removal of a process from the processor. It is an important part of multiprogramming in operating system.Process Scheduling AlgorithmsProcess scheduling algorithms are used to handle the selection of a process for the processor or distribute resources maong processes.Some of the process scheduling algorithms are given as follows −First Come First ServedThis algorithm handles the processes in the order they arrive in the ready queue. FCFS is the simplest scheduling algorithm. There is no preemption in FCFS and so no ... Read More

Details about the zombie, orphan and daemon processes are given as follows −Zombie ProcessesA zombie process is a process whose execution is completed but it still has an entry in the process table. Zombie processes usually occur for child processes, as the parent process still needs to read its child’s exit status. Once this is done using the wait system call, the zombie process is eliminated from the process table. This is known as reaping the zombie process.A diagram that demonstrates the creation and termination of a zombie process is given as follows −Zombie processes don't use any system resources ... Read More

In Operating System, the fork() system call is used by a process to create another process. The process that used the fork() system call is the parent process and process consequently created is known as the child process.Details about these are given as follows −ProcessA process is an active program i.e a program that is under execution. It is more than the program code as it includes the program counter, process stack, registers, program code etc. Compared to this, the program code is only the text section.A process changes its state as it executes. This state partially depends on the ... Read More

A deadlock happens in operating system when two or more processes need some resource to complete their execution that is held by the other process.In the above diagram, the process 1 has resource 1 and needs to acquire resource 2. Similarly process 2 has resource 2 and needs to acquire resource 1. Process 1 and process 2 are in deadlock as each of them needs the other’s resource to complete their execution but neither of them is willing to relinquish their resources.Coffman ConditionsA deadlock occurs if the four Coffman conditions hold true. But these conditions are not mutually exclusive.The Coffman ... Read More

Both process and thread are related to each other and quite similar as these are the independent sequence of execution. The basic difference between a process and a thread is that a process takes place in different memory spaces, whereas a thread executes in the same memory space. Read through this article to find out how a process is different from a thread, in the context of operating systems. Let's start with some basics of threads and processes. What is a Process? A process is an active program, i.e., a program that is under execution. It is more ... Read More

Message passing model and shared memory model are models of interprocess communication. Details about these are given as follows −Message Passing Process Communication ModelMessage passing model allows multiple processes to read and write data to the message queue without being connected to each other. Messages are stored on the queue until their recipient retrieves them. Message queues are quite useful for interprocess communication and are used by most operating systems.A diagram that demonstrates message passing model of process communication is given as follows −In the above diagram, both the processes P1 and P2 can access the message queue and store ... Read More

Race conditions, Critical Sections and Semaphores are an key part of Operating systems. Details about these are given as follows −Race ConditionA race condition is a situation that may occur inside a critical section. This happens when the result of multiple thread execution in critical section differs according to the order in which the threads execute.Race conditions in critical sections can be avoided if the critical section is treated as an atomic instruction. Also, proper thread synchronization using locks or atomic variables can prevent race conditions.Critical SectionThe critical section in a code segment where the shared variables can be accessed. ... Read More

Monitors and semaphores are used for process synchronization and allow processes to access the shared resources using mutual exclusion. However, monitors and semaphores contain many differences. Details about both of these are given as follows −MonitorsMonitors are a synchronization construct that were created to overcome the problems caused by semaphores such as timing errors.Monitors are abstract data types and contain shared data variables and procedures. The shared data variables cannot be directly accessed by a process and procedures are required to allow a single process to access the shared data variables at a time.This is demonstrated as follows:monitor monitorName { ... Read More