Operating Systems Overview

Single-User, Multi-Tasking OS

• Allows a single user to access the computer, but can run multiple programs simultaneously
• Examples include Windows 95, 98, and XP, macOS, and Linux
• Key advantages:
  • Improved multitasking capabilities
  • Improved user interaction
• Limitations:
  • Limited multitasking capabilities
  • Limited user interaction
  • Limited hardware support

Kernel

• Embedded in main memory, interacts with hardware
• Written in a low-level language

Processor

• Central Processing Unit (CPU), the core of the computer

Device Handler

• Manages device requests
• Operates in a continuous cycle
• Follows the First-In-First-Out (FIFO) principle

Spooler

• Manages simultaneous peripheral output
• Runs computer processes and outputs results

User Interface

• Creates a simple environment for users to interact with the computer system
• Provides communication between users and hardware/software

Multi-user Operating Systems

• Distributed System
• Time sliced system
• Multiprocessor system
• These systems allow multiple users to access the same system simultaneously

Key Differences Between Preemptive and Non-Preemptive Scheduling

• Preemptive scheduling: Interrupts a running process, while non-preemptive scheduling does not.
• Fairness and Equity: Preemptive scheduling ensures these qualities, while non-preemptive scheduling can lead to starvation.
• Context Switching Overhead: Preemptive scheduling has higher overhead, while non-preemptive scheduling has lower overhead.

Process Scheduling Algorithms

• First-Come-First-Served
• Shortest Job First
• Priority Scheduling
• Round Robin
• Multilevel Feedback Queue

Resource Allocation

• Assigning system resources such as memory, I/O devices, and CPU time to different processes

Process Synchronization

• Processes interact with each other through synchronization mechanisms:
  • Semaphores
  • Monitors
  • Message Passing

Process Communication

• Processes communicate with each other through various mechanisms:
  • Semaphores
  • Monitors
  • Message Passing

Process Termination

• A process can be voluntarily terminated, be terminated by another process, or be terminated by the operating system.
• A parent process can terminate its child process.
• Reasons for termination:
  • Process completion
  • Error or exception
  • Resource exceedance
  • User request
  • System shutdown
  • Parent process termination

Parent Process Responsibilities

• Creating the child process
• Providing resources
• Monitoring the child process

Process Tree

• A hierarchical structure where each child process can create its own child processes.

Process Termination Cleanup Steps

• Resource deallocation
• Context switching
• PID deallocation

Resource Overhead and Resource Exceedance

• Resource Overhead: The resources required to manage and maintain a system, process, or application.
• Resource Exceedance: Occurs when a system, process, or application uses more resources than are available or allocated to it.

Process Control Block (PCB)

• Contains information about a process:
  • Process ID (PID)
  • Process state (running, waiting, ready)
  • Priority
  • Memory limits
  • List of open files
  • CPU scheduling information
  • Process counter (program counter)
  • Registers
  • Memory limits

Context Switching

• The process of saving the state of a running process and loading the state of another process.
• Steps:
  • Save the current state
  • Restore the new state
  • Update the PCB
  • Switch to the new process

Context Switching Optimization

• Increase CPU resources:
  • Multi-core processors
  • Parallel processing
  • Increasing clock speed
• Minimize context size:
  • Reducing process size

This quiz covers the fundamental concepts of single-user and multi-user operating systems. It includes details on kernels, processors, device handlers, and user interfaces, as well as the advantages and limitations of each system. Test your knowledge on how these components interact within a computer system.