Page 65 - DCAP103_Principle of operating system

Principles of Operating Systems

Notes Message-Passing System: Message passing in computer science is a form of communication
used in parallel computing, object-oriented programming, and interprocess communication.
Process Control Block (PCB): The PCB is a certain store that allows the operating systems to
locate key information about a process.
Process Counter: Program instructions uniquely identified by their program counters (PCs)
provide a convenient and accurate means of recording the context of program execution and
PC-based prediction techniques have been widely used for performance optimizations at the
architectural level.
Process Management: The operating system manages many kinds of activities ranging from
user programs to system programs like printer spooler, name servers, file server, etc. Each of
these activities is encapsulated in a process.

Process Scheduling: The problem of determining when processors should be assigned and to
which processes is called processor scheduling or CPU scheduling.

Process State: The process state consist of everything necessary to resume the process execution
if it is somehow put aside temporarily.

Synchronization: In computer science, especially parallel computing, synchronization means
the coordination of simultaneous threads or processes to complete a task in order to get correct
runtime order and avoid unexpected race conditions.
Thread: A thread is a single sequence stream within in a process. Because threads have some
of the properties of processes, they are sometimes called lightweight processes. In a process,
threads allow multiple executions of streams.
2.8 Review Questions

1. What is a process?
2. What about process states?

3. What is a process control block?
4. How do processes inter-communicate?

5. How do processes synchronize their activity?
6. How do processes protect critical data (Critical sections)?
7. Consider the interprocess-communication scheme where mailboxes are used:

( a) Suppose a process P wants to wait for two messages, one from mailbox A and one
from mailbox B. What sequence of send and receive should it execute?

( b) What sequence of send and receive should P execute if P wants to wait for one
message from mailbox A or from mailbox B (or from both)?

8. What are the benefits and the detriments of each of the following? Consider both the
systems and the programmers’ levels.

(a) Direct and indirect communication
(b) Symmetric and asymmetric communication
(c) Automatic and explicit buffering

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