22516 Operating System Unit 3 Notes PDF

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                              Process management is one of the core functions of an operating system. It's about how the OS handles the creation, scheduling, and termination of processes. Let's delve into the details.

1. Definition of a Process: A process can be thought of as a program in execution. It includes the current values of the program counter, registers, and variables, as well as the code itself. Each process is typically executed in its own process address space.

 

2. Process Life Cycle: The state of a process changes as it moves through various stages:

• New: The process is being created.
• Ready: The process is ready to be assigned to a processor and run.
• Running: The process is currently being executed.
• Waiting: The process is waiting for an event or resource.
• Terminated: The process has finished execution.

 

3. Process Control Block (PCB): For every process, the OS maintains a data structure known as the Process Control Block. It contains information about the process such as:

• Process ID
• Process State (new, ready, etc.)
• Program Counter
• CPU Registers
• CPU Scheduling Information
• Memory Management Information
• List of I/O devices allocated to the process

 

4. Process Scheduling: The OS decides which of the ready processes should be moved to the running state. Several algorithms can be employed for this:

• First-Come-First-Serve (FCFS)
• Shortest Job Next (SJN)
• Priority Scheduling
• Round Robin (RR)
• Multilevel Queue Scheduling

 

5. Context Switching: When the CPU switches from one process to another, it saves the state of the old process and loads the saved state for the new process. This operation is called a context switch.

 

6. Process Creation & Termination:

• Processes can be created by other processes using system calls. A parent process can create child processes.
• Processes are terminated when they've finished execution or when they are killed either by their own actions or by others.

 

7. Inter-process Communication (IPC): Processes often need to communicate with each other. This can be done using various mechanisms like:

• Message Passing: Processes communicate with each other without sharing variables.
• Shared Memory: A common memory location is shared by multiple processes for communication.

 

8. Process Synchronization: When processes communicate, they often need to be synchronized to avoid conflicts and ensure data integrity. Mechanisms include:

• Semaphores: A high-level synchronization primitive.
• Locks: Prevent more than one process from accessing a critical section.
• Monitors: A synchronization tool that wraps up the shared variable/condition and the methods to access them in one package.

 

9. Deadlock Management: Deadlocks occur when processes are waiting for resources that are held by other processes. They are in a state where they can't move forward. The OS must:

• Prevent: Implement a strategy to ensure deadlocks never occur.
• Avoid: Allow conditions that might cause a deadlock but ensure they don't occur in practice.
• Detect: Allow deadlocks to occur but have a mechanism to detect them.
• Recover: After detection, recover the system from the deadlock.

 

Conclusion: Process management is an essential aspect of an OS, ensuring efficient utilization of the CPU, providing multitasking capabilities, and allowing processes to work harmoniously without conflicts. The effectiveness of process management directly impacts the system's performance and user experience.