Operating Systems Process Management

Definition: Coordination of processes in a computer, managing their execution and resources.
Process: A program in execution, including the program code and its current activity.
States of a Process:
- New: The process is being created.
- Ready: The process is waiting to be assigned to a processor.
- Running: Instructions are being executed.
- Waiting: The process is waiting for an event to occur.
- Terminated: The process has finished execution.
Process Control Block (PCB): Data structure used to store all information about a process, including state, program counter, CPU registers, and memory management information.
Context Switching: The process of storing the state of a process so that it can be resumed later, allowing multiple processes to share the CPU.

Definition: Management of computer memory, allocating and deallocating memory space as needed by processes.
Key Concepts:
- Physical vs. Virtual Memory: Physical memory refers to actual hardware (RAM), while virtual memory allows the use of disk space to extend available memory.
- Paging: Memory management scheme that eliminates the need for contiguous allocation of physical memory and eliminates fragmentation.
- Segmentation: Divides the process into different segments based on logical division (e.g., functions, objects).
Memory Allocation Strategies:
- Contiguous Allocation: Allocating a single contiguous block of memory.
- Paging: Dividing memory into fixed-size pages.
- Segmentation: Allocating variable-sized segments.

Definition: Manages how data is stored and retrieved on storage devices.
Components:
- File: A collection of related data, identified by a name.
- Directory: A structure that contains file names and other directories.
- File System Types: FAT, NTFS, ext3/ext4, HFS+.
Operations:
- Creation: Creating a new file or directory.
- Deletion: Removing a file or directory.
- Reading/Writing: Accessing and modifying file data.
- Permissions: Managing access control to files (read, write, execute).
Mounting: The process of making a file system accessible at a certain point in the directory structure.

Definition: Determines the order in which processes are executed by the CPU.
Types of Scheduling:
- Preemptive: Allows a process to be interrupted and moved to a ready state (e.g., Round Robin, Shortest Job First).
- Non-preemptive: Once a process starts execution, it runs to completion (e.g., First-Come, First-Served).
Common Algorithms:
- First-Come, First-Served (FCFS): Processes are executed in the order they arrive.
- Shortest Job First (SJF): Prioritizes processes with the shortest execution time.
- Round Robin (RR): Each process gets a small time slice in a cyclic order.
- Priority Scheduling: Processes are scheduled based on priority levels; can be preemptive or non-preemptive.
Performance Metrics:
- Turnaround Time: Total time taken from submission to completion.
- Waiting Time: Total time a process spends waiting in the ready queue.
- Throughput: Number of processes completed in a given time.

Coordination of computer processes, managing execution and resources.
A process is an executing program, including the code and current activity.
States of a Process:
- New: Creation phase.
- Ready: Waiting for CPU assignment.
- Running: Currently executing instructions.
- Waiting: Awaiting an event completion.
- Terminated: Execution finished.
Process Control Block (PCB) stores process information such as state, program counter, CPU registers, and memory management.
Context Switching allows multiple processes to share a CPU by saving and restoring process states.

Management of memory allocation and deallocation for processes.
Physical Memory refers to actual RAM; Virtual Memory extends memory using disk space.
Paging eliminates fragmentation by using fixed-size pages for memory allocation.
Segmentation divides processes into logical segments like functions or objects.
Memory Allocation Strategies include:
- Contiguous Allocation: Single block allocation.
- Paging: Fixed-size divisions.
- Segmentation: Variable-sized allocations.

Determines the order of process execution by the CPU.
Types of Scheduling:
- Preemptive: Processes can be interrupted (e.g., Round Robin, Shortest Job First).
- Non-preemptive: Processes run to completion once started (e.g., First-Come, First-Served).
Common Scheduling Algorithms:
- First-Come, First-Served (FCFS): Processes execute in arrival order.
- Shortest Job First (SJF): Prioritizes processes with the shortest execution time.
- Round Robin (RR): Each process receives time slices in a cyclic manner.
- Priority Scheduling: Based on process priority; can be preemptive or non-preemptive.
Performance Metrics to evaluate scheduling:
- Turnaround Time: Total time from submission to completion.
- Waiting Time: Duration in the ready queue.
- Throughput: Number of completed processes in a specific timeframe.