Independent processes operate concurrently without affecting each other, while cooperating processes can impact one another. Inter-process communication (IPC) allows processes to share information, improve computation speed, and share resources. The two main types of IPC are shared memory and message passing. Shared memory uses a common memory region for fast communication, while message passing involves establishing communication links and exchanging messages without shared variables. Key considerations for message passing include direct vs indirect communication and synchronous vs asynchronous messaging.

2. 
Adeel Rasheed
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3. 
 Independent Processes:
Operating concurrently on a
systems are those that can neither affect other processes
or be affected by other processes.
 Cooperating Processes:
Are those that can affect or
be affected by other processes.
IPC

4. 
 Mechanism for allows processes to communicate and
to synchronize their actions.
IPC

5. 
 Information sharing: Several processes may need
to access the same data (such as stored in a file.)
 Computation speedup: A task can offer be run
faster if it is broken into subtasks and distributed
among different processes.
 Resource Sharing: Sharing Hardware, memory etc
Why We Use IPC

6. 
 Modularity: It may be easier to organize a complex
task into separate subtasks, then have different
processes or threads running each subtask.
 Convenience: An individual user can run several
programs at the same time, to perform some task.
Why We Use IPC

7. 
 Shared Memory systems.
 Message Passing systems.
Types/Ways of IPC

8. Shared Memory
 Allows multiple processes to share virtual memory
space.
 Fastest but not necessarily the easiest (synchronization-
wise) way for processes to communicate with one
another. Process A Process B
0x30000
0x50000
0x50000
0x70000Shared memory
region

9. 
Shared Memory

10. 
 There are two processes: Producer and
Consumer.
 Producer produces some item and Consumer
consumes that item.
 The two processes shares a common space or
memory location known as buffer where the item
produced by Producer is stored and from where the
Consumer consumes the item if needed.
Producer-Consumer
problem

11. 
 There are two version of this problem: first one is
known as unbounded buffer problem in which
Producer can keep on producing items and there is
no limit on size of buffer, the second one is known as
bounded buffer problem in which producer can
produce up to a certain amount of item and after that
it starts waiting for consumer to consume it. The
pseudo code are given below:
Unbounded Buffer Problem

12. 
 We will discuss the bounded buffer problem. First, the
Producer and the Consumer will share some common
memory, then producer will start producing items. If
the total produced item is equal to the size of buffer,
producer will wait to get it consumed by the
Consumer. Similarly, the consumer first check for the
availability of the item and if no item is available,
Consumer will wait for producer to produce it. If there
are items available, consumer will consume it.
Bounded Buffer Problem

13. 

14. 
 In a Message passing system there are no shared variables.
IPC facility provides two operations for fixed or variable
sized message:
 send(message)
 receive(message)
 If processes P and Q wish to communicate, they need to:
 establish a communication link
 exchange messages via send and receive
Message-Passing Systems

15. 

16. 
 There are key issues to be resolved in message
passing systems as further explored in the next
subsections:
 Direct or indirect communication ( naming )
 Synchronous or asynchronous communication
Key Issues

17. 
 With direct communication the sender must know the
name of the receiver to which it wishes to send a
message. There is a one-to-one link between every
sender-receiver pair.
 Symmetric communication, the receiver must also
know the specific name of the sender from which it
wishes to receive messages.
 Asymmetric communications, this is not necessary.
Direct Communication

18.  Indirect communication uses shared mailboxes, or
ports. Multiple processes can share the same mailbox or
boxes.
 Only one process can read any given message in a
mailbox. Initially the process that creates the mailbox is
the owner, and is the only one allowed to read mail in
the mailbox, although this privilege may be transferred.
 The OS must provide system calls to create and delete
mailboxes, and to send and receive messages to/from
mailboxes.
Indirect communication

19. 
 synchronous messaging involves a client that waits
for the server to respond to a message. Messages are
able to flow in both directions, to and from.
 Asynchronous messaging involves a client that does
not wait for a message from the server. An event is
used to trigger a message from a server. So even if
the client is down, the messaging will complete
successfully. Asynchronous Messaging means that, it
is a one way communication and the flow of
communication is one way only.
Synchronous or asynchronous
communication

20. 