Operating System: Core Functions and Objectives

• An operating system is a program that serves as an intermediary between a user and computer hardware.
• Its purpose is to make computers user-friendly and secure for running applications.

Goals

• Simplify the execution of user programs and problem-solving.
• Provide a convenient computer system.
• Utilize computer hardware efficiently.

Objectives

• Enhance the use of the computer.
• Use resources efficiently.
• Enable effective development, testing, and addition of new features without service interruption.
• Manage system resources, ensuring fair sharing among processes and users.

Core Functions

• Resource Management: Allocating and deallocating CPU time, memory, and I/O devices.
• Process Management: Creating, scheduling, and terminating processes for efficient execution.
• Memory & File Management: Implementing strategies to organize file storage, including paging, segmentation, and virtual memory.
• Device Management: Interfacing with hardware via drivers and managing communication between peripherals and the system.
• Security and Protection: Enforcing access controls and safeguarding resources from unauthorized access.

History and Evolution

Mainframes (1950s)

• Large, expensive computers requiring manual job scheduling.
• Early systems like IBM 701 & 1BM 704 ran on GM-NAA I/O.
• Programmers wrote programs on paper, punched them on cards, and submitted card decks for processing.

Batch Processing System

• Jobs submitted in batches to maximize utilization of computing resources.
• It eliminates the need for user interaction during processing.

Time Sharing System (1960s)

• Interactive computing and remote terminal access.
• Allows multiple users to interact with the computer simultaneously.
• Multiprogramming enabled multiple active processes.
• Programmers could interact with the computer system directly.

Personal Computers (1970s-1980s)

• Transition to smaller, user-friendly computers with graphical interfaces.
• Examples include Apple Macintosh and early versions of Windows.

Modern OS Features

• Distributed systems.
• Real-time (RTOS).
• Embedded systems.
• Mobile operating systems.

Current Trends

• Virtualization.
• Containerization.
• Increased focus on security.
• Increased focus on energy efficiency.
• Increased focus on user-centric design.

Operating System Structure

• Consist of two parts: Kernel and Shell.

Kernel

• The core that directly controls the computer hardware.
• Performs OS services and hides hardware details from users and applications.
• Resides in main memory for immediate access.

Shell

• Acts as the command interpreter
• Serves as the interface between users and the kernel.
• Users enter commands which are then interpreted to use the service of the kernel.
• Types: Command-Line Interface (CLI) and Graphical User Interface (GUI).

System Types & Operating Systems

Mainframe Computers

• Large, high-performance systems for handling vast amounts of data simultaneously.
• IBM z/OS: Tailored for IBM hardware, supporting multiprocessors and high security.
• z/VM: Designed for virtualizing mainframe environments.

Servers

• Specialized computers managing network resources and providing services to other computers.
• Linux: Used in server environments for its stability, security, and flexibility
• Windows Server: Provides file and printing services, web hosting, and active directory management.

Personal Computers (PCs)

• General-purpose devices for individual use.
• Microsoft Windows: Dominant OS with a user-friendly interface and wide software support.
• MacOS: Developed by Apple, with a sleek interface and integration with Apple hardware.

Mobile Devices

• Portable computing systems for wireless communication and mobility.
• Android: Based on Linux, designed for touchscreen devices.
• iOS: Developed by Apple, powering iPhones and iPads, known for user experience and integration.

Embedded Systems

• Specialized for dedicated functions within larger systems, emphasizing real-time operation and reliability.
• Embedded Linux: Customized version of Linux for embedded applications, offering flexibility and a range of development tools.
• VxWorks: Real-time OS.
• FreeRTOS: Open-source RTOS for embedded devices, offering a minimalistic footprint.

Real-Time Operating Systems (RTOS)

• Processes data within strict timing constraints.
• RTEMS: Open-source RTOS for embedded systems, supporting multi-processor systems.
• QNX: Commercial RTOS with high reliability, used in automotive and industrial applications.

Distributed Systems

• Multiple computers communicating and coordinating actions for common goals.
• Google's Android: Supports distributed computing principles.
• Apache Hadoop: Provides a scalable platform for big data applications.

Hypervisor-Based Systems

• Virtualization platforms allowing multiple virtual machines (VMs) to run on a single physical machine.
• Type 1 Hypervisor (Bare-metal): Runs directly on the hardware managing VMs.
• VMware ESXi: Runs directly on server hardware, managing VMs with resource utilization and high availability.
• Microsoft Hyper-V: Integrated into Windows Server and Windows operating systems, allowing VM creation, management, and dynamic memory allocation.
• Type 2 Hypervisor (Hosted): Runs on top of a host OS, using host resources to create and manage VMs.
• VirtualBox: Free, open-source hypervisor.
• VMware Workstation: Powerful hypervisor providing advanced features for running multiple operating systems.

Hypervisor

• Provides virtual machines on one computer, and controls how CPU and memory are shared.

Virtual Machine (VM)

• Computer inside a computer.
• Like a separate machine but uses the resources of the main system.

System Software and System Programming

Software

• Instructions telling the computer what to do.
• Written in C++ and Java.

Application Software

• Programs accomplishing specialized tasks.

Document Production Software

• Compose, edit, print, and publish documents electronically, like Microsoft Word, Google Docs, and LibreOffice Writer

Business Software

• Finance, Accounting,
• Software such as QuickBooks, FreshBooks, Wave, Tax Preparation such as TurboTax H&R Block, TaxSlayer

Multimedia Software

• Manipulate images, sound, and video such as Adobe Photoshop, GIMP, Affinity Photo, and Audacity Adobe Audition, FL Studio

Entertainment Software

• Programs for entertainment, media playback and gaming.

System Software

• Manipulates basic operations of a computer system.
• Examples: OS, compilers, debuggers, linkers, loaders, interpreters, and text editors.

System Programming

• Developing system software, it requires a strong knowledge of computer hardware architecture.

System Software

• Can be written in machine, assembly, or high-level languages.

Machine Language

• The computer understands
• Low-level language.

Assembly Language

• Programming made easier using mnemonics.

High-level Programming Language

• Easier to use because commands resemble English
• C++, Java, Visual Basic.

Machine Language

• Language that is natural to the computer.
• Uses 0's and 1's.
• Difficult to program with, high-level is preffered

High Level Language

• Instructions are first converted into machine language.
• Compiler does the translation

Advantages of High-Level Over Assemble Language

• Easier to learn and use.
• Has pre-defined functions and subroutine
• Not machine dependent.

Advantages of Assemble Language Over High-Level

• Executable code is compact – executions fasters.
• Not constrained with certain programming conventions, nor rigid coding restrictions.
• Has instructions that allow programmers more direct control over memory access.
• Some system software programmers use assembly language-based subroutines to supplement high-level language capabilities

Language Translators

• Convert high-level program or assembly language program into machine language.
• They convert machine code and assemble the source and executables.
• Assemblers translate assembly
• Compilers translate and create executables
• Interpreters converts program high-level code into CPU readable machine language

Linkers and Loaders

• The system software combines or links the code and libraries that make an executable code.
• Linker is the editor
• Compilers don't always produce executables
• Modular Programming helps compilers by test code independently
• Mod codes are then converted to objects, and combined with Linker

Address Binding

• Assigns symbolic references to memory locations
• Uses physical address system

Loader Techniques

• Absolute Loading: Has memory addresses for variables ready
• Relocatable Loading: Memory addresses are created before loading
• Dynamic Run-Time Loading: Happens only when its immediately needed when it is needed.

Operating System Architectures

• Defines how the system interacts.
• Determins how the balance, security, and modularity is organized.
• It defines how everything gets managed

OS Components

• Kernel integrates with hardware directly
• Service manages the Kernel, drives, drivers, etc.
• Interface is used for system applications with Shells and GUI

Architech Types

Monolithic Architecture- single stone type of design Microkernel Architecture- only needs to provide core services Hybrid Architecture- a balance to speed and modularity Exokernel Architecture- Securely multiple hardware resources and delegates resources to user-space libraries. Layered Architecture- Organizes functionality into distinct layers