Communicating Sequential Processes - C A R Hoare
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Basic idea: multiple concurrent processes can synchronize with each
other by synchronizing their I/O i.e., I/O happens only when process A
specifically states that it is ready to send data to process B and
when process B specifically states that it is ready to recieve data
from A. If only one happens without the other, the corresponding
process is put on a wait queue.

Guarded commands: normal program statement + guard (Boolean
expr). Executed only if guard evaluates to true.

Alternative guarded command; repeated guarded commands; guard with
input from a specific process;

Producer-Consumer Problem: Producer(P) --> Buffer(X) --> Consumer(C) X
is bounded. P sends output command to X when it is ready to send
data. P will wait if X did not issue an input command. C issues an
input command when it wants more data. X has multiple guarded commands
which check whether there is anything in the buffer and if so sends an
output command to C, and issues an input command for P if P is ready
with data.

Dining Philosophers Problem

CSP seems to be similar to blocking message passing

Advantages: Conceptually simple, and works for many synchronization
problems

Disadvantages: Explicit naming of processes needed, and no buffering
(always blocking)