Operating Systems Chapter 3: Processes

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Questions and Answers

What is the term used for a program that is currently executing and has progress in a sequential manner?

Job

Thread

Task

Process (correct)

Which of the following states indicates that a process is waiting for an event to occur?

Running

New

Waiting (correct)

Terminated

Which of these is NOT part of a Process Control Block (PCB)?

Program counter

I/O status information

CPU registers

Stack pointer (correct)

What information does a Process Control Block not provide?

User interface graphics (D) Signup and view all the answers

Which queue consists of all processes that are currently ready and waiting to execute?

Ready queue (B) Signup and view all the answers

Which state represents a process that has completed its execution?

Terminated (A) Signup and view all the answers

What is the purpose of process migration between various queues?

To optimize CPU resource allocation (A) Signup and view all the answers

Which of the following is an example of a device queue?

Queue of processes waiting for an I/O device (D) Signup and view all the answers

Where is a process placed when it issues an I/O request?

It is placed in an I/O queue (C) Signup and view all the answers

What does the long-term scheduler primarily control?

The degree of multiprogramming (D) Signup and view all the answers

What is the role of a medium-term scheduler?

It selects which process to remove from memory by swapping (D) Signup and view all the answers

Which scheduler is invoked most frequently to manage process execution?

Short-term scheduler (D) Signup and view all the answers

What is required for P and Q to communicate effectively?

An established communication link (D) Signup and view all the answers

In direct communication, which process is needed to send a message?

Only the sender must name the recipient (D) Signup and view all the answers

What happens during a context switch?

Old process state is saved and new state is loaded (D) Signup and view all the answers

What characterizes an I/O-bound process?

It requires frequent access to I/O resources (B) Signup and view all the answers

How many links exist between each pair of communicating processes?

Exactly one link per pair (D) Signup and view all the answers

Which statement best describes a communication link?

It can be either unidirectional or bi-directional (B) Signup and view all the answers

What does the term 'process creation' refer to?

The formation of a tree of child processes from a parent (D) Signup and view all the answers

Which scheduler would be the slowest in terms of invocation frequency?

Long-term scheduler (B) Signup and view all the answers

What characteristic describes the recipient in an asymmetric addressing scheme?

The recipient receives messages from any process without naming the sender (B) Signup and view all the answers

What is a key characteristic of the resources shared between a parent process and its child processes?

Parent and child processes share different address spaces. (D) Signup and view all the answers

What does the fork system call do in UNIX?

Creates a new process. (B) Signup and view all the answers

Under what condition may a parent process terminate its child processes!

The parent process is exiting. (B) Signup and view all the answers

What distinguishes cooperating processes from independent processes?

Cooperating processes can affect or be affected by one another. (D) Signup and view all the answers

What is the primary function of the receive operation in Interprocess Communication (IPC)?

To consume messages sent by other processes. (C) Signup and view all the answers

Which of the following describes the bounded-buffer scenario in the producer-consumer problem?

A fixed buffer size restricts the number of items that can be stored. (C) Signup and view all the answers

Which of the following is a primary reason for providing an environment supporting process cooperation?

To facilitate information sharing. (C) Signup and view all the answers

What happens when a process executes its last statement and requests the operating system to terminate it?

It is removed from any system list along with its PCB. (D) Signup and view all the answers

What is required for processes to communicate using indirect communication?

They must share a mailbox. (D) Signup and view all the answers

Which of the following describes a property of a communication link?

A link may be associated with multiple processes. (A) Signup and view all the answers

What operation is NOT included in the indirect communication model?

Send messages to direct contacts. (D) Signup and view all the answers

In which scenario might a blocking send operation occur?

The sender waits for the message to be received. (C) Signup and view all the answers

Which type of message passing is considered asynchronous?

Non-blocking send where the sender continues. (D) Signup and view all the answers

What describes a zero capacity buffering system?

Sends must wait for a receiver to be available. (D) Signup and view all the answers

Which statement about mailbox sharing is true?

Only one process can send to a mailbox at a time. (C) Signup and view all the answers

Which is NOT a primitive operation in indirect communication?

delete(A, message) (C) Signup and view all the answers

Study Notes

Process Concept

Operating systems execute various programs, categorized as batch systems for jobs and time-shared systems for user tasks.
A process is a program in execution, progressing sequentially and comprising a program counter, stack, and data section.

Process State

Process states include:
- New: process being created.
- Running: instructions are being executed.
- Waiting: process waiting for an event or resources.
- Ready: process waiting to be assigned to a CPU.
- Terminated: process execution completed.

Process Control Block (PCB)

PCB is a data structure representing a process in memory, storing various information including:
- Current process state
- Program counter
- CPU registers
- Scheduling information
- Memory management data
- Accounting info
- I/O status data

Process Scheduling Queues

Job queue: contains all processes in the system.
Ready queue: contains processes ready for execution in main memory.
Device queues: contains processes awaiting I/O devices.

Schedulers

Long-term scheduler: selects processes for the ready queue from the job queue; invoked infrequently.
Short-term scheduler: selects the next process to be executed; invoked very frequently.
Medium-term scheduler (MTS): handles process swapping in and out of memory for better performance.

Context Switch

A context switch occurs when the CPU switches to a different process, requiring the saving of the old process's state and loading of the new one.
Context-switch time introduces overhead, as the system does not perform useful work during the switch.

Process Creation

Parent processes create child processes, forming a process tree, with each child having one parent.
Resources may be shared between processes, but address spaces are separate, preventing changes in one from affecting the other.
UNIX example: fork system call creates a new process; exec replaces the child's memory with a new program.

Process Termination

A process terminates when it executes its last statement and requests termination, leading to resource deallocation and removal from system lists.
Parents may also terminate child processes under specific conditions, leading to cascading termination in some operating systems.

Cooperating Processes

Independent processes operate without affecting each other, while cooperating processes can influence one another for purposes such as:
- Information sharing
- Speed-up in computation
- Modularity
- Convenience of programming

Producer-Consumer Problem

Involves cooperating processes where a producer creates information consumed by a consumer.
Unbounded-buffer: has no limit on buffer size, allowing producers to process without waiting.
Bounded-buffer: has a fixed size, requiring producers to wait if the buffer is full.

Interprocess Communication (IPC)

IPC mechanisms enable processes to communicate and synchronize actions, primarily through message passing.
Operations include send(message) and receive(message) involving either fixed or variable length messages.
Establishes communication links, which can be physical or logical.

Direct Communication

Requires processes to name each other explicitly for message exchange:
- send(P, message) sends a message to process P.
- receive(Q, message) receives a message from process Q.

Indirect Communication

Involves mailboxes (or ports) for message exchange, characterized by:
- Unique identifiers for mailboxes.
- Permitting communication only between processes sharing a mailbox.
- Links may be unidirectional or bi-directional.

Buffering

Message queuing can be implemented with:
- Zero capacity: sender waits for receiver.
- Bounded capacity: finite queue length; sender waits if full.
- Unbounded capacity: infinite length; sender never waits.

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Explore the key concepts of processes in operating systems through this quiz. You'll learn about process scheduling, interprocess communication, and the differences between batch and time-shared systems. Test your knowledge on the important aspects of processes and their management.