Process

threads within the Process will share the memory space.

Different processes will have different memory space.

Overview

The term process in the context of operating systems refers to a fundamental concept that encapsulates the execution of a program. It includes the program's code, its current activity, and its execution state. Understanding processes is crucial for grasping how operating systems manage and execute tasks.

Key Characteristics

• Program vs. Process:

  • Program: A static collection of instructions stored in a file.
  • Process: A dynamic instance of a program in execution, including the program counter, CPU registers, and memory.

• Process State:

  • New: The process is being created.
  • Running: Instructions are being executed.
  • Waiting: The process is waiting for an event (e.g., I/O completion).
  • Ready: The process is waiting to be assigned to a processor.
  • Terminated: The process has finished execution.

• Process Control Block (PCB):

  • A data structure used by the operating system to store all the information about a process. It includes the process state, program counter, CPU registers, memory limits, and accounting information.

Process Management

• Process Creation:

  • Processes are created by the OS through system calls such as fork() in Unix/Linux or CreateProcess() in Windows.

• Process Scheduling:

  • The OS uses scheduling algorithms (e.g., Round Robin, Priority Scheduling) to allocate CPU time to processes, ensuring efficient CPU utilization and fair distribution of resources.

• Inter-Process Communication (IPC):

  • Mechanisms that allow processes to communicate and synchronize their actions. Common IPC methods include pipes, message queues, semaphores, and shared memory.

• Process Termination:

  • Processes terminate when they complete their execution or are terminated by the OS. The termination status is often communicated back to the parent process.

Process Synchronization

• Race Conditions:

  • Occur when multiple processes attempt to modify shared data concurrently, leading to unpredictable outcomes.

• Critical Sections:

  • Sections of code that access shared resources and must be executed by only one process at a time.

• Synchronization Mechanisms:

  • Mutexes, Semaphores, Monitors, and Condition Variables are used to enforce mutual exclusion and ensure orderly access to shared resources.

Practical Considerations

• Concurrency vs. Parallelism:

  • Concurrency: Multiple processes or threads make progress, but not necessarily simultaneously.
  • Parallelism: Multiple processes or threads execute simultaneously on multiple cores or processors.

• Deadlock:

  • A condition where a set of processes are blocked forever, waiting for resources held by each other. Strategies like Deadlock Detection, Prevention, and Avoidance are used to handle deadlocks.

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