Operating System Process Management

Operating System: Process Management

Definition of Process:
- A process is a program in execution, which includes the program code, current activity, and the process state.
Process States:
- New: The process is being created.
- Ready: The process is ready to run and is waiting for CPU time.
- Running: The process is currently being executed by the CPU.
- Waiting: The process is waiting for some event (e.g., I/O completion).
- 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.
- Contains:
  - Process ID (PID)
  - Process state
  - Program counter
  - CPU registers
  - Memory management information
  - I/O status information
Process Scheduling:
- The method by which the operating system decides the order in which processes will access the CPU.
- Types of scheduling:
  - Long-term scheduling: Determines which processes are admitted to the system.
  - Short-term scheduling: Decides which of the ready processes will be executed next.
  - Medium-term scheduling: Swaps processes in and out of memory to ensure efficient operation.
Scheduling Algorithms:
- First-Come, First-Served (FCFS): Processes are scheduled in the order they arrive.
- Shortest Job Next (SJN): The process with the smallest execution time is scheduled next.
- Priority Scheduling: Processes are scheduled based on priority levels.
- Round Robin (RR): Each process is assigned a fixed time slice in a cyclic order.
Inter-Process Communication (IPC):
- Mechanisms that allow processes to communicate with each other.
- Common IPC methods include:
  - Message Passing: Processes send and receive messages to exchange information.
  - Shared Memory: Processes share a segment of memory for communication.
Concurrency:
- Multiple processes executing simultaneously.
- Issues include race conditions, deadlocks, and resource starvation.
Process Synchronization:
- Techniques to ensure that processes operate in a coordinated manner.
- Common methods include:
  - Locks: Prevent multiple processes from accessing a resource simultaneously.
  - Semaphores: Signaling mechanisms to control access to resources.
  - Monitors: High-level synchronization constructs that allow safe access to shared resources.
Context Switching:
- The process of storing the state of a currently running process and loading the state of the next process to be executed.
- Involves saving and loading PCBs, registers, and memory maps.
Process Creation and Termination:
- Creation: Initiated by system calls such as fork() in Unix/Linux.
- Termination: Processes can terminate normally or abnormally; requires cleanup of resources.

Understanding these concepts of process management is essential for grasping how operating systems manage multiple tasks efficiently.

Definition of Process

A process is an executing program that includes code, current activity, and its state.

Process States

New: Process is in the creation phase.
Ready: Process is prepared to run and awaiting CPU allocation.
Running: Process is actively being executed by the CPU.
Waiting: Process awaits some event, such as I/O operation completion.
Terminated: Process has completed execution.

Process Control Block (PCB)

A vital data structure maintained by the operating system that holds information about each process.
Contains:
- Process ID (PID): Unique identifier for the process.
- Process state: Current state of the process.
- Program counter: Next instruction to execute.
- CPU registers: Context information required for execution.
- Memory management information: Data related to the process's memory usage.
- I/O status information: Status of process I/O operations.

Process Scheduling

Mechanism by which the operating system decides the process execution order for CPU access.
Long-term scheduling: Determines which processes enter the system.
Short-term scheduling: Selects which ready process executes next.
Medium-term scheduling: Manages swapping processes in and out of memory.

Scheduling Algorithms

First-Come, First-Served (FCFS): Processes execute in the order of arrival.
Shortest Job Next (SJN): The process with the least estimated execution time runs next.
Priority Scheduling: Processes are executed based on assigned priority levels.
Round Robin (RR): Each process receives a fixed time slice cyclically.

Inter-Process Communication (IPC)

Techniques that enable processes to communicate and synchronize operations.
Message Passing: Sending and receiving messages between processes for information exchange.
Shared Memory: Direct access to a common memory area for data exchange.

Concurrency

Allows multiple processes to execute simultaneously, raising challenges such as race conditions, deadlocks, and resource starvation.

Process Synchronization

Techniques aimed at ensuring processes operate together without conflict.
Locks: Mechanisms that prevent multiple processes from accessing the same resource simultaneously.
Semaphores: Signaling tools that control access to shared resources.
Monitors: Advanced synchronization features that manage safe access to shared data.

Context Switching

Process of saving the state of the currently executing process and loading the state of the next scheduled process.
Involves management of PCBs, CPU registers, and memory maps.

Process Creation and Termination

Creation: Initiated using system calls like fork() in Unix/Linux environments.
Termination: Can occur normally or abnormally, necessitating resource cleanup.