Operating Systems: Processes Overview

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Questions and Answers

What is the primary system call for creating a new process in UNIX?

init

spawn

fork (correct)

createProcess

Which of the following is NOT a typical condition that causes a process to terminate?

Fatal error

Normal exit

Timeout (correct)

Killed by another process

Which state is a process in when it is unable to run due to waiting for an external event?

Blocked (correct)

Terminated

Ready

Running

What happens to a child process immediately after it is created using fork?

It has the same memory image as the parent. Signup and view all the answers

In process hierarchies, which process can create additional processes?

Any process Signup and view all the answers

Which of the following best explains a running state of a process?

The process is currently executing on the CPU. Signup and view all the answers

What is the result of a process blocking for input?

The scheduler picks another process to run. Signup and view all the answers

Which system event does NOT directly result in process creation?

Resource allocation by the OS Signup and view all the answers

What is the primary function of a process in a computing environment?

To abstract the execution of a program Signup and view all the answers

What concept describes the illusion of parallelism in a system with a single CPU?

Pseudo parallelism Signup and view all the answers

What happens to the program counter when a process is switched out in a multiprogramming system?

It is saved as the logical program counter Signup and view all the answers

Which statement accurately describes processes in a multiprogramming system?

Only one process can be active at any time Signup and view all the answers

How do processes in a system differ from programs?

A process refers to an executing program while a program is static Signup and view all the answers

What mechanism is primarily responsible for switching between different processes in a multiprogramming environment?

Context switching Signup and view all the answers

In a computing system, what role does the logical program counter play for a process?

It reflects the current state of the process execution Signup and view all the answers

When multiple processes are being managed by a single CPU, what allows for different processes to make progress?

Time slicing Signup and view all the answers

Study Notes

Processes Overview

A process is an abstraction representing a running program, enabling (pseudo) concurrent operations on a single CPU.
Examples include a web server handling multiple requests or an operating system managing several processes like email clients and word processors.

Process Management

In multiprogramming systems, the CPU rapidly switches between processes, ensuring that, at any moment, only one process is actively running.
This switching creates an illusion of parallelism, referred to as pseudo parallelism.

The Process Model

All runnable software, including the OS, is organized into sequential processes, with each considered an instance of an executing program.
Each process maintains its own virtual CPU, while the real CPU alternates among processes through multiprogramming.
There is a single physical program counter; during execution, the logical program counter of the current process loads into it.

Process Independence

Each process has a unique flow of control, enabling independent execution of multiple processes.
At any given time, only one process is actively using the CPU, while others may progress at other intervals.

Differentiating Program and Process

A program is a static set of instructions (like a recipe), whereas a process is the active execution of a program with input, output, and state (like a cook completing the recipe).
Running the same program multiple times results in separate processes.

Process Creation Events

Processes can be created due to:
- System initialization
- Execution of a process creation system call
- User requests for new processes
- Initiation of batch jobs

UNIX Process Creation

The primary system call for creating processes in UNIX is fork, generating an identical clone of the calling process.
Post-fork, both parent and child processes share the same memory, environment strings, and open files.
Typically, the child process executes execve to run a new program after the fork, allowing for file descriptor manipulation beforehand for input/output redirection.

Process Termination Conditions

Processes can terminate under typical conditions:
- Normal exit (voluntary)
- Error exit (voluntary)
- Fatal error (involuntary)
- Termination by another process (involuntary)

Process Hierarchies

In certain systems, the relationship between parent and child processes can lead to hierarchies, where a child can create additional processes.
In UNIX, a process and its descendants form a process group, enabling collective signal handling for operations such as keyboard signals.

Process States

A process can exist in one of three states:
- Running: Actively using the CPU.
- Ready: Runnable but temporarily paused for another process.
- Blocked: Unable to run until an external event occurs (e.g., waiting for input).
The distinction exists between logical blocking (waiting for input) and CPU allocation by the OS.

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Description

This quiz covers the fundamental concepts of processes in operating systems, exploring how they enable concurrent operations. Key examples include multi-tasking environments and web servers managing multiple requests. Test your understanding of CPU switching and process management in multiprogramming systems.