Inter-process communication (IPC) allows processes to communicate and synchronize. Common IPC methods include pipes, message queues, shared memory, semaphores, and mutexes. Pipes provide unidirectional communication while message queues allow full-duplex communication through message passing. Shared memory enables processes to access the same memory region. Direct IPC requires processes to explicitly name communication partners while indirect IPC uses shared mailboxes.

1. INTER PROCESS
COMMUNICATION (IPC)

2. IPC
• Inter-process 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.

3. SYNCHRONIZATION
• 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.
• Mutual Exclusion: Mutual exclusion requires that only one process
thread can enter the critical section at a time.
• Barrier: A barrier does not allow individual processes to proceed until
all the processes reach it.
• 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.

4. APPROACHES

5. • A pipe is a data channel that is unidirectional. Two pipes can be used
to create a two-way data channel between two processes.
• Message Passing:
• It is a mechanism for a process to communicate and synchronize.
• Using message passing, the process communicates with each other
without resorting to shared variables.
PIPES

6. MESSAGE QUEUES
• A message queue is a linked list of
messages stored within the kernel.
• It is identified by a message queue
identifier.
• This method offers communication
between single or multiple processes
with full-duplex capacity.
• Message queues are quite useful for
inter process communication and are
used by most operating systems.

7. 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.
• Shared memory is a memory shared between
two or more processes that are established
using shared memory between all the
processes.
• This type of memory requires to protected from
each other by synchronizing access across all
the processes.

8. DIRECT COMMUNICATION
• In the Direct Communication, each process that wants to communicate
must explicitly name the recipient or sender of the communication.
• In this, process that want to communicate must name the sender or
receiver.
1. A pair of communicating processes must have one link between them.
2. A link (generally bi-directional) establishes between every pair of
communicating processes.

9. INDIRECT COMMUNICATION
• Pairs of communicating processes have shared mailboxes.
• Link (uni-directional or bi-directional) is established between pairs of
processes.
• Sender process puts the message in the port or mailbox of a receiver
process and receiver process takes out (or deletes) the data from the
mailbox.
• A link can communicate with many processes. The link may be bi-
directional or unidirectional.

10. FIFO
• FIFOs (first-in, first-out) are a
variation on a pipe that creates a more
flexible communication structure.
• FIFOs work by attaching a filename
to the pipe. For this reason, FIFOs are
also called named pipes as opposed to
the anonymous pipes discussed
previously.
• FIFOs are created by one process that
calls mkfifo().