Operating Systems Lecture 3: Process Concept

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Questions and Answers

What does a process primarily represent in an operating system?

A program stored on a disk

An active program in execution (correct)

A passive program waiting to execute

A series of stored commands

Which section of a process is responsible for holding local variables and function parameters?

Data section

Heap

Stack (correct)

Text section

What state is a process in when it is waiting for an event to occur?

Ready

Running

New

Waiting (correct)

Which of the following represents the correct state transition when a process is created?

New to Ready Signup and view all the answers

What is the purpose of the Process Control Block (PCB)?

To contain information about each process Signup and view all the answers

Which statement best describes the execution of instructions within a single process?

Execution occurs in a sequential fashion. Signup and view all the answers

What does the 'Terminated' state signify in the context of process execution?

The process has completed execution. Signup and view all the answers

Which component of a process contains memory allocated at runtime?

Heap Signup and view all the answers

What is the purpose of the program counter in a process?

To indicate the location of the next instruction to execute Signup and view all the answers

Which of the following refers to the information that a CPU scheduling system maintains?

Priorities and scheduling queue pointers Signup and view all the answers

What does accounting information in a process control block typically include?

CPU time used and clock time elapsed since start Signup and view all the answers

What happens to a process that is waiting for an event such as I/O?

It migrates to the wait queue. Signup and view all the answers

Which statement about multiple threads of control within a process is true?

Multiple threads allow for independent execution sequences within a single process. Signup and view all the answers

What is the result of a context switch?

The CPU switches from one process to another. Signup and view all the answers

Which queue contains all processes that are ready and waiting to execute?

Ready queue Signup and view all the answers

When might a process migrate to the wait queue?

When it is waiting for an I/O operation to complete. Signup and view all the answers

What happens to a child process if its parent process is terminated without invoking the wait() system call?

The child process becomes a zombie. Signup and view all the answers

Which system call allows a parent process to retrieve the termination status of a child process?

wait() Signup and view all the answers

What is a potential reason for a parent process to abort a child process?

The parent process has exited. Signup and view all the answers

What characterizes a cooperating process in interprocess communication?

They can share data and affect each other’s execution. Signup and view all the answers

What is a major challenge with shared memory in interprocess communication?

Synchronization of processes accessing shared memory is required. Signup and view all the answers

Which of the following statements is true regarding cascading termination of processes?

All child processes are terminated if the parent process terminates. Signup and view all the answers

What type of interprocess communication model allows user processes to control the communication?

Shared memory Signup and view all the answers

What is the outcome if a process does not have a parent waiting for its termination?

The process will become an orphan. Signup and view all the answers

In the bounded-buffer model, what happens when the buffer is full?

The producer must wait until a buffer is available. Signup and view all the answers

What limitation exists in the shared memory solution for the bounded-buffer problem?

It can only use BUFFER_SIZE-1 elements effectively. Signup and view all the answers

How does the producer know when to produce a new item in the bounded-buffer solution?

It waits until there is space in the buffer. Signup and view all the answers

What role does the integer counter play in the modified buffer-filling solution?

It tracks the number of produced and consumed items. Signup and view all the answers

What condition causes a consumer to wait in the bounded-buffer model?

There are no items left in the buffer. Signup and view all the answers

What happens when the counter reaches BUFFER_SIZE in the producer process?

Production is temporarily halted. Signup and view all the answers

Which operation is NOT part of the IPC facilities for message passing?

create(link) Signup and view all the answers

In Android's process hierarchy, which type of process is the least important?

Empty process Signup and view all the answers

How does multitasking in early versions of iOS differ from versions after iOS4?

Subsequent versions support limited multitasking. Signup and view all the answers

What must processes P and Q do to communicate effectively?

Establish a communication link. Signup and view all the answers

Which statement is true regarding background processes in iOS?

They have specific limits on their operation. Signup and view all the answers

What is the purpose of a counter in producer-consumer processes?

To manage the number of items in the buffer. Signup and view all the answers

Which type of Android process has the highest priority?

Foreground process Signup and view all the answers

Study Notes

Process Concept

An operating system runs various programs known as processes.
A process is defined as a program in execution, requiring sequential progress of instructions.
Key components of a process include:
- Program code: Refers to the text section.
- Current activity: Includes the program counter and processor registers.
- Stack: Contains temporary data such as function parameters and local variables.
- Data section: Holds global variables.
- Heap: Memory allocated dynamically during runtime.

Program vs. Process

A program is a passive entity stored on disk, whereas a process is active in memory.
Execution of a program may be initiated through graphical interfaces or command lines.
One program can correspond to multiple processes, especially with multiple users.

Process State

A process can exist in several states during its execution:
- New: The process is being created.
- Running: Instructions are being actively executed.
- Waiting: The process is waiting for a specific event.
- Ready: The process awaits CPU assignment.
- Terminated: The process has completed its execution.

Process Control Block (PCB)

PCB contains vital information for each process, known as the task control block:
- Process state: Status of the process (e.g., running, waiting).
- Program counter: Points to the next instruction to execute.
- CPU registers: Stores process-specific register contents.
- Scheduling information: Includes priorities and pointers to the scheduling queue.
- Memory-management: Details on memory allocation for the process.
- Accounting information: Tracks CPU usage and elapsed time since the process started.
- I/O status information: Lists I/O devices allocated and open files.

Process Scheduling

Process scheduler is responsible for selecting processes for CPU execution, aiming to maximize CPU use.
Maintains different queues:
- Ready queue: Processes ready and waiting in main memory.
- Wait queues: Processes waiting for events like I/O.

Context Switch

A context switch occurs when the CPU shifts from executing one process to another.
Ensures all status data is returned from child to parent processes and deallocates resources used by the process.
The parent may terminate child processes using the abort() system call for various reasons.

Process Termination

When a process terminates, all its children may also be terminated, leading to cascading termination.
Parent processes can wait for child terminations using the wait() system call, which provides status and process id (pid).
Processes with no waiting parent become zombies, while those whose parent terminated without wait become orphans.

Interprocess Communication (IPC)

Processes can be independent or cooperating, with cooperating processes sharing data and affecting each other.
Reasons for cooperation include information sharing, computation speedup, modularity, and convenience.
Two models for IPC:
- Shared memory: Processes communicate through a designated area of memory.
- Message passing: Processes exchange messages without shared variables.

Producer-Consumer Problem

A common example of cooperating processes involves a producer creating information consumed by a consumer.
Variations:
- Unbounded-buffer: No practical limit on buffer size; the producer never waits.
- Bounded-buffer: Fixed buffer size; the producer waits if the buffer is full.

IPC: Shared Memory

Communication management is controlled by user processes rather than the operating system.
Synchronization issues arise when processes access shared memory.

IPC: Message Passing

Processes communicate without shared variables.
Requires establishing communication links and exchanging messages, either fixed or variable in size.

Android Process Hierarchy

Mobile operating systems like Android manage processes based on importance, with specific types ranked from most to least important:
- Foreground process
- Visible process
- Service process
- Background process
- Empty process

Multitasking in Mobile Systems

Early mobile systems allowed only one active process, suspending others.
Starting from iOS4, limited multitasking was introduced:
- Single foreground process is user-controlled.
- Multiple background processes allowed with specified limitations.
Subsequent iOS versions support richer multitasking, including split-screen functionality on larger devices.

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Description

This quiz covers the fundamental concepts of processes in operating systems, detailing what defines a process and its components. Explore how programs execute in a sequential manner and the various parts that constitute a process. Perfect for anyone studying the basics of operating systems.