Problem $4(20)$

The functions Send$(.)$ and Receive$(.)$ are used for sending and receiving messages for inter$-$process communication, respectively.

Send$($void $*$sendbuf$,$ int nelems, int dest$)$: Send nelems elements saved in buffer sendbuf to the destination process dest.

Receive$($void $*$recvbuf$,$ int nelems, int source$)$: Receive nelems elements saved in buffer recvbuf, which is sent from the process source.

We have two different methods for inter$-$process communication.

Method $1$: The process executing send$(.)$ is blocked when the other process is not executing the corresponding receive$(.).$

Method $2$: The process executing send$(.)$ puts the message in buffer, which is transmitted to the receiver side via hardware, and returns, but the process executing receive$(.)$ is blocked when the message is not available. This method does not block the sender$,$ but it may block the receiver.

Consider the following two cases $1)$ and $2)$ for communications between process $0$ and process $1.$

Case $1)$

P$0$:

Receive$($&a$,1,1$