Operating system: functions and resource management

• An operating system deals with a computer's CPU, RAM, I/O devices, and long-term storage
• An OS manages computer hardware and software, providing essential services for application programs
• An OS serves as a bridge between users and computer hardware

Interface and Resource Management

• An OS provides the interface between users and computer hardware
• An OS manages how applications access computer resources like disk drives, CPU, memory, input/output devices, and network interfaces
• An OS manages multiple users and programs

Key Functions of and OS

• Process Management: Handles execution of multiple programs
• Memory Management: Allocates and optimizes system memory usage
• File System Management: Organizes and secures files and data storage
• Device Management: Controls input and output hardware components
• Security & Access Control: Safeguards data and system integrity
• User Interface: Provides interaction methods like GUI or CLI

Single-User vs. Multi-User OS

• A Single-User OS supports only one user at a time; examples include Windows and macOS
• A Multi-User OS allows multiple users to access the system simultaneously; examples include Unix and Linux

Network and Distributed OS

• A Network Operating System (NOS) manages network resources, facilitates communication between connected devices, and provides centralized control over a network; examples include Windows Server, Linux Server, and Novell Netware
• A Distributed Operating System (DOS) coordinates a collection of independent computers and presents them as a single system to the user, improving performance and fault tolerance; examples include Amoeba, Sprite, and Google's Fuchsia

Mobile OS Characteristics

• Mobile OSs are designed to run on mobile devices and optimize battery life and mobile connectivity
• Unlike desktop OS, mobile OS are designed for touch gestures like swiping and tapping
• Mobile OS efficiently manages power consumption to prolong battery life
• Mobile OS uses app stores for software distribution and installation
• Mobile OS Implements security measures such as sandboxing, app permissions, and encryption to protect user data
• Mobile OSs support cellular networks, Wi-Fi, Bluetooth, GPS, and NFC for communication and location services.
• Mobile OS optimize RAM and storage usage to ensure smooth performance

Core Concepts of Operating Systems

• Process Management is a core OS function that deals with the execution of programs, ensuring multiple processes can run efficiently without conflicts

Key Concepts in Process Management

• A process is a running instance of a program that requires system resources
• Process Lifecycle includes: New, Ready, Running, Waiting, and Terminated states
• Scheduling Algorithms prioritize and execute processes; common algorithms include First Come First Serve (FCFS), Round Robin, and Priority Scheduling

Importance of Process Management

• Process management ensures fair allocation of CPU time, prevents deadlocks, and optimizes system performance by balancing CPU utilization

Memory Management

• Memory Management in an OS handles and optimizes the computer's memory (RAM and virtual memory), ensuring programs have the necessary memory to function
• The OS manages primary memory (RAM) and extends it using virtual memory when RAM is full
• Paging & Segmentation are techniques that divide memory into fixed-size or variable-size blocks to improve efficiency
• Allocation Strategies: Fixed Partitioning divides memory into fixed blocks and Dynamic Partitioning adjusts memory partitions based on process needs
• Memory management ensures system stability, efficiency, and multitasking capability

File System Management

• File System Management refers to how an OS organizes, stores, retrieves, and manages files on a storage device, ensuring data is accessible, structured, and secure

Key Aspects of Storage

• The OS uses directory structures to organize files
• Each file has attributes like name, size, type, and permissions.

Common File Systems

• NTFS is commonly used in Windows and supports security, compression, and large file sizes
• FAT32 is an older file system with broad compatibility but limited security and file size
• ext4 is commonly used in Linux and offers journaling for reliability and efficiency

Security and Integrity

• Data Organization keeps files structured and easy to locate
• Security implements access control to prevent unauthorized modifications.
• Efficiency optimizes storage use and speeds up data retrieval
• Reliability prevents file corruption and ensures data integrity

Security and Protection Mechanisms

• User Authentication involves verifying user identity before granting access to the system using passwords, biometrics, or two-factor authentication
• Access Control Policies define who can access what data and resources within the system; models include Role-Based Access Control (RBAC) and Discretionary Access Control (DAC)
• Data Encryption ensures sensitive information is stored and transmitted securely

Components of an Operating System

• Kernel: The core of the OS that directly interacts with hardware, responsible for process management, memory management, and device control
• Shell: Acts as an interface between the user and the OS; examples include Command-Line Interface (CLI) and Graphical User Interface (GUI)
• File System: Manages data storage and organization, defining how files are stored, retrieved, and accessed; examples include FAT32, NTFS (Windows), and ext4 (Linux)
• Device Drivers: Software that allows the OS to communicate with hardware components like printers, keyboards, graphics cards, and storage devices

Common Operating Systems and Their Applications

• Windows has a friendly user GUI, extensive software support, and is used for personal and business computing
• Linux: Open-source, highly customizable, used for servers, security, and embedded systems
• macOS: Optimized for Apple hardware, stable performance and is used for creative work and multimedia editing
• Unix: Multi-user, secure, stable and is used for enterprise systems and servers
• Android: Touch-based, open-source, mainly for mobile devices
• iOS: Secure, optimized for Apple devices, used for Apple mobile devices

Kernel Architectures

• Monolithic Kernel: All essential OS functions are integrated into a single large program, resulting in fast performance but potentially less security and stability; examples include Linux, Unix, and early versions of Windows
• Microkernel: Only the most essential functions run in kernel mode, while other components operate in user mode as separate processes, making it more modular, secure, and fault-tolerant; examples include QNX, MINIX, and macOS (XNU hybrid kernel)

Different Kernel Architectures

• QNX: Real-time OS using a microkernel architecture, improving system stability and security, and is used in embedded systems.
• MINIX: Microkernel-based OS, initially designed for educational purposes, used in embedded environments like Intel's Management Engine
• macOS: Hybrid kernel (XNU) that combines elements of both, balancing security, stability, and efficiency.

Windows Hybrid Kernel

• Windows uses a hybrid kernel architecture that combines aspects of both monolithic and microkernel designs
• The Windows NT kernel includes essential OS components while still allowing modular drivers and services

Layered and Modular OSs

• Layered OS is designed with a hierarchical structure, simplifying debugging and maintenance
• Modular OS allows components to be dynamically loaded or removed, offering greater flexibility, scalability, customization and enhanced security
• THE Operating System by Technische Hogeschool Eindhoven is an example of a layered OS while Windows NT is an example of a modular OS

THE Operating System

• The THE Operating System has a strict hierarchical structure, where each layer had a specific role and communicated only with adjacent layers
• Layer 0 handled hardware interaction and CPU scheduling, Layer 1 handled memory management, Layer 2 handled process communication, Layer 3 handled input/output device management, and Layer 4 handled user programs
• This structured design influenced modern OS architectures

Virtualization

• Virtualization creates a virtual version of an OS, server, storage device, or network resource
• Virtualization enables multiple OS environments to run on a single physical machine using a hypervisor
• Virtual Machines (VMs) like VMware, VirtualBox, and Microsoft Hyper-V allow users to run different OSes on the same hardware

Cloud Based OS

• Cloud-based OS operates over the internet rather than being installed on a local machine
• This shifts OS management and storage to remote cloud servers, allowing users to access their OS
• Chrome OS is a cloud-centric OS that relies on web applications
• AWS Cloud OS & Azure Virtual Desktop are cloud platforms that provide scalable OS environments

Modern Computing Benefits

• Virtualization improves hardware efficiency, enhances security, and supports system isolation
• Cloud Computing reduces dependency on physical storage and provides high accessibility and scalability