Operating Systems Overview

Operating System Overview

• A computer system is composed of hardware, software, and users.
• Software is categorized as system software or application software.
• System software manages and controls hardware, while application software facilitates user tasks.
• Hardware provides mechanisms to ensure proper system operation and prevent user program interference.
• Operating system design is a complex task requiring well-defined goals.
• Goals guide algorithm and strategy choices.
• Operating systems must be built in pieces with defined inputs, outputs, and functions.
• Operating systems for handheld computers aim for user-friendly interfaces.
• Operating systems can be designed for convenience, efficiency, or a combination of both.

What Is An Operating System?

• An operating system manages all computer system resources.
• It is a software component responsible for managing and coordinating computer activities and resource sharing.
• It acts as an intermediary between the user and computer hardware, managing communication between components, applications, and the user.
• Key tasks include:
  • Continuously monitoring resources.
  • Enforcing policies to determine resource allocation.
  • Allocating resources.
  • De-allocating resources.
  • Directing data flow through the CPU, guiding memory access, data storage, and display.
  • Monitoring user logins, resource usage, and access requests (acting as an accountant).

Functions of an Operating System

• Makes a computer system more convenient to use.
• Enables efficient use of computer system resources.
• Allows the development, testing, and implementation of new system functions without interrupting service.

Evolution of Operating Systems

• 1st Generation (1945-1955): Programmers directly operated the machine.
• 2nd Generation (1955-1965): Batch Operating System.
  • Used punched cards or paper tapes as input.
  • Jobs were processed sequentially without user interaction.
  • Efficiency was measured by throughput and turnaround time.
• Second Generation Continued: Single User Operating System.
  • Controlled by one user at a time.
  • Examples: DOS, Palm OS, Windows CE, Inferno, Newton OS, Internet Tablet OS.
• 3rd Generation (1965-1985): Multiuser Operating System.
  • Allowed a single computer (often mainframe) to handle simultaneous input, output, and processing requests from multiple users.
  • Prioritized processing requests.
  • Examples: Linux, Unix, Windows 2000, Windows XP.
• 3rd Generation Continued: Multi-programming Operating System (also called Multi-tasking).
  • Enabled multiple software processes to run simultaneously.
  • Could be either cooperative or preemptive:
    • Cooperative multitasking hands control over to a program and waits for it to return control.
    • Preemptive multitasking maintains OS control and manages program execution.
  • Examples: Unix, Windows NT, Mac OS, Windows 95, Windows 9X.
• 3rd Generation Continued: Time Sharing Operating System (also called Interactive Systems).
  • Provided direct user interaction via keyboard commands.
  • Delivered computer services directly to the user through a terminal.
  • Posed security and access control challenges.
  • Provided immediate feedback with response times measured in minutes or seconds.
• 3rd Generation Continued: Personal Computer Operating System.
  • Used for personal computers supporting a single user environment.
  • Simpler than mainframe operating systems.
  • Prioritized user-friendliness.
  • Examples: Linux, Macintosh, MS-DOS, Windows 2000.
• 4th Generation (1985-Present): Real Time Operating System (RTOS).
  • Uses time as a key parameter for operation.
  • Considered multi-tasking, intended for real-time applications (e.g., programmable thermostat, appliance controllers, mobile phones).
  • Can be Hard Real-Time (strict time requirements) or Soft Real-Time (more flexible response time).
  • Examples: JavaFx Mobile, BeRTOS, INtime RTOS for Windows, iRMX, OS-9.
• 4th Generation Continued: Embedded Operating System.
  • Implanted within equipment to control its operation.
  • Performs dedicated functions.
  • Examples: BlackBerry OS, embedded Linux, iPhone OS.
• 4th Generation Continued: Network Operating System (NOS) (also called Server Operating Systems, Distributed Operating System, or Loosely Coupled System).
  • Enables computers to communicate through network cable or wireless transmission.
  • Focuses on managing network resources.

File Manager

• Enables users and applications to work with files.
• Provides services related to:
  • Creating, deleting, reading, and modifying files.
  • Moving data between files.
  • Backing up and recovering files.
  • Rapidly accessing files.
  • Ensuring file integrity and security.

Security Manager

• Protects data and resources from unauthorized access.
• Guarantees data and message authenticity.
• Defends systems against network attacks.
• Prevents users from accidentally or intentionally interfering with each other.
• Enforces security policies.
• Tracks resource access requests.

System Calls & Interrupts

• Processes inside a computer system communicate with the processor via system calls.
• The processor handles these communications using methods like polling and interrupts.
• Polling: The processor checks each connected device for requests.
• Interrupts: Devices signal the processor when they need attention, interrupting the processor's current task.
  • Hardware and software interrupts can occur, prompting the processor to pause its current task to handle the request.
  • Processor remembers the interrupted process's state to resume operation later.
  • If multiple interrupts occur, they are handled based on priority.

This quiz covers the fundamental concepts of operating systems, including the distinction between system software and application software. It explores the role of hardware in system operation and the various design goals for creating effective operating systems. Test your understanding of how operating systems manage resources and user interactions.