Process B

Figure 1 - Shared Memory and Message Passing
ii) Messaging Passing Method

Now, We will start our discussion for the communication between processes via message
passing. In this method, processes communicate with each other without using any kind of

of shared memory. If two processes ‏1ج‎ and p2 want to communicate with each other, they

proceed as follow:

« Establish a communication link (if a link already exists, no need to establish it again.)
« Start exchanging messages = using basic primitives.
We need at least two primitives:

— send(message, destinaion) or send(message)
— receive(message, host) or receive(message)

Receiving
Process

ye

Processid Message

The message size can be of fixed size or of variable size. if it is of fixed size, it is easy for
OS designer but complicated for programmer and if it is of variable size then it is easy for

programmer but complicated for the OS designer. A standard message can have two parts: