Operating Systems Process Concepts

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Questions and Answers

What occurs during a context switch?

The operating system completes its operations without interruption.

The system executes a new process without saving the old state.

The state of the running process is saved and the new process state is loaded. (correct)

The CPU runs multiple processes simultaneously.

Which factor can lengthen the context-switch time?

Using a single set of registers per CPU. (correct)

Simple operating systems with fewer PCB entries.

Having fewer processes in the ready state.

Enhanced hardware that provides multiple sets of registers.

What is true about pre-emption in the context of multiprogramming?

It can lead to starvation of processes needing continuous CPU access.

It increases the overall time for all processes to complete.

Processes are allowed to run until completion without interruption.

Processes are forcefully removed from the CPU to allocate time to others. (correct)

How is the degree of multiprogramming defined?

The maximum number of processes that can reside in the ready state. Signup and view all the answers

Which of the following statements is accurate regarding context switching?

Complexity in the OS leads to longer context switch times. Signup and view all the answers

What is a process in the context of an operating system?

A program in execution Signup and view all the answers

What must happen for a program to become a process?

The executable file is loaded into memory Signup and view all the answers

Which of the following is NOT a component of a process?

User interface Signup and view all the answers

In which type of system are user programs or tasks executed simultaneously?

Time-shared systems Signup and view all the answers

Which of the following sections of a process contains temporary data such as function parameters and local variables?

Stack Signup and view all the answers

What is the primary function of the program counter in a process?

To hold the next instruction to execute Signup and view all the answers

Which of the following best describes 'interprocess communication'?

The exchange of data between processes Signup and view all the answers

What does the term 'heap' refer to in the context of a process?

Memory dynamically allocated during runtime Signup and view all the answers

What is one of the primary reasons for terminating a child process?

The child process has exceeded allocated resources. Signup and view all the answers

What system call is typically used for process termination?

exit() Signup and view all the answers

Which condition can lead to the termination of a process due to resource limitations?

The process requires more memory than is available. Signup and view all the answers

What happens to a child process if its parent process is terminated?

The child process will also be terminated. Signup and view all the answers

What is cascading termination in relation to process management?

All child processes, grandchildren, etc., are terminated. Signup and view all the answers

What information is typically NOT included in a Process Control Block (PCB)?

User credentials Signup and view all the answers

What is the primary purpose of process scheduling in an operating system?

To maximize CPU use and enable time sharing Signup and view all the answers

A process may be terminated if it tries to access which of the following?

A resource it is not allowed to use Signup and view all the answers

What occurs if an I/O failure happens in relation to process termination?

The process will be terminated. Signup and view all the answers

Which of the following best describes a running process in terms of its state?

The process is actively executing instructions Signup and view all the answers

What system call might a parent process use to wait for the termination of a child process?

wait() Signup and view all the answers

In a multiprogramming operating system, what is a key factor that allows multiple processes to share the CPU?

Time multiplexing Signup and view all the answers

Which of the following is NOT part of the CPU registers information in a PCB?

Process execution time Signup and view all the answers

What happens to a process during a context switch?

Its execution is paused and its PCB is updated Signup and view all the answers

What characteristic is essential for a multiprogramming operating system?

Loading multiple processes in memory simultaneously Signup and view all the answers

Which of the following best describes I/O status information in a PCB?

Identification of I/O devices allocated to the process Signup and view all the answers

What occurs when both the sender and receiver are blocked in a message-passing scenario?

A rendezvous is created. Signup and view all the answers

Which type of send operation allows the sender to continue without waiting for the recipient to receive the message?

Non-blocking send Signup and view all the answers

What is the consequence of a zero capacity queue in message buffering?

The sender must wait for the recipient to receive the message. Signup and view all the answers

In the context of blocking and non-blocking operations, which of the following is true about blocking receive operations?

They block the receiver until a message is available. Signup and view all the answers

What type of message passing is characterized by a sender being blocked until the message is received?

Blocking send Signup and view all the answers

Which statement correctly describes the behavior of a non-blocking receive operation?

It can return either a valid message or a null message. Signup and view all the answers

How can a producer-consumer problem be simplified in a message-passing context?

Through the use of blocking sends and receives. Signup and view all the answers

Which of the following combinations results in a rendezvous during message passing?

Blocking send and blocking receive Signup and view all the answers

Study Notes

Process Concept

A program being executed is called a process.
A process is an active entity that represents the basic unit of work in a system.
A process is comprised of multiple parts:
- Program code (text section)
- Current activity (program counter, processor registers)
- Stack (temporary data, function parameters, return addresses, local variables)
- Data section (global variables)
- Heap (dynamically allocated memory)
A program is a passive entity stored on disk (executable file).
A program becomes a process when loaded into memory.

Process State

A diagram of the process state depicts a process moving between states:
- New: The process is being created.
- Running: The process is currently using the CPU.
- Waiting: The process is waiting for an event, such as I/O completion.
- Ready: The process is waiting to be assigned to the CPU.
- Terminated: The process has completed execution.

Process Control Block (PCB)

The PCB (Process Control Block), also known as the task control block, holds information associated with each process.
The PCB contains:
- Process state
- Program counter (location of the next instruction to execute)
- CPU registers (contents of all process-centric registers)
- CPU scheduling information (priorities, scheduling queue pointers)
- Memory management information (memory allocated to the process)
- Accounting information (CPU usage, elapsed time, time limits)
- I/O status information (I/O devices allocated, list of open files)

Process Scheduling

Process scheduling optimizes CPU usage and facilitates time-sharing by quickly switching processes on and off the CPU.
The process scheduler decides which process runs next.
Process scheduling is a key component of multiprogramming operating systems.

Context Switch

A context switch occurs when the CPU transitions from one process to another.
The system saves the state of the old process and loads the saved state of the new process.
The context switch involves saving and restoring the contents of the PCB.
Context switch time is overhead, as the system isn't performing useful work during the switch.
Faster hardware, like CPUs with multiple sets of registers, can reduce context switch time.

Multiprogramming

Multiprogramming allows multiple processes to reside in memory simultaneously.
Two types of multiprogramming:
- Pre-emption: A process is forcefully removed from the CPU (time-sharing, multitasking).
- Non-pre-emption: Processes run until completion without interruption.
The degree of multiprogramming indicates the maximum number of processes that can be in the ready state.

Process Termination

A process can be terminated due to various reasons:
- Normal completion of execution
- Parent process request
- Resource violation (e.g., attempting to write to a read-only file)
- I/O failure
- Parent process termination (cascading termination)
- Memory shortage
The wait() system call allows a parent process to wait for a child process to terminate.

Synchronization

Message passing is a method of inter-process communication (IPC) and can be blocking or non-blocking.
Blocking message passing is synchronous:
- Blocking send: The sender process blocks until the message is received.
- Blocking receive: The receiver process blocks until a message is available.
Non-blocking message passing is asynchronous:
- Non-blocking send: The sender sends the message and continues execution.
- Non-blocking receive: The receiver receives either a valid message or a null message.

Buffering

Buffering is a technique used in message passing involving a queue of messages attached to a communication link.
Buffering options include:
- Zero capacity: No messages can be queued, requiring the sender to block until the receiver processes the message.

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Description

Explore the fundamental concepts of processes in operating systems. Understand how a program becomes an active process, the different states of a process, and the components that make up a process. Test your knowledge of this essential topic in system management.