UNIT 2 – INTERPROCESS COMMUNICATION
Interprocess communication is the mechanism provided by the
operating system that allows processes to communicate with each other.
This communication could involve a process letting another process know
that some event has occurred or the transferring of data from one process to
another.
Synchronization in Interprocess Communication
Synchronization is a necessary part of interprocess communication. It is
either provided by the interprocess control mechanism or handled by the
communicating processes. Some of the methods to provide synchronization
are as follows −
• Semaphore
A semaphore is a variable that controls the access to a common
resource by multiple processes. The two types of semaphores are
binary semaphores and counting semaphores.
• Mutual Exclusion
Mutual exclusion requires that only one process thread can enter the
critical section at a time. This is useful for synchronization and also
prevents race conditions.
• Barrier
A barrier does not allow individual processes to proceed until all the
processes reach it. Many parallel languages and collective routines
impose barriers.
• Spinlock
This is a type of lock. The processes trying to acquire this lock wait in
a loop while checking if the lock is available or not. This is known as
busy waiting because the process is not doing any useful operation
even though it is active.
Approaches to Interprocess Communication
The different approaches to implement interprocess communication are
given as follows −
• Pipe
A pipe is a data channel that is unidirectional. Two pipes can be used
to create a two-way data channel between two processes. This uses
standard input and output methods. Pipes are used in all POSIX
systems as well as Windows operating systems.
• Socket
The socket is the endpoint for sending or receiving data in a network.
This is true for data sent between processes on the same computer or
data sent between different computers on the same network. Most of
the operating systems use sockets for interprocess communication.
• File
A file is a data record that may be stored on a disk or acquired on
demand by a file server. Multiple processes can access a file as
required. All operating systems use files for data storage.
• Signal
Signals are useful in interprocess communication in a limited way.
They are system messages that are sent from one process to another.
Normally, signals are not used to transfer data but are used for remote
commands between processes.
• Shared Memory
Shared memory is the memory that can be simultaneously accessed
by multiple processes. This is done so that the processes can
communicate with each other. All POSIX systems, as well as Windows
operating systems use shared memory.
• Message Queue
Multiple processes can read and write data to the message queue
without being connected to each other. Messages are stored in the
queue until their recipient retrieves them. Message queues are quite
useful for interprocess communication and are used by most operating
systems.
