Operating Systems: Theory, Concepts and Types

Introduction to Operating Systems (OS)

• Caitriona Nic Lughadha is the lecturer.
• Lectures are on Thursdays from 9 am to 11 am, and labs are on Fridays from 10 am to 11 am.
• 50% of the assessment is from Mid Semester Continuous Assessment and 50% from the End of Semester Exam.

Module Learning Outcomes

• Discuss of the theory and concepts behind operating systems
• Compare the strengths and weaknesses of modern operating systems
• Apply tools to understand OS theory and concepts
• Demonstrate system utility use and operating system investigation

Module Content Overview

• The module covers Definition of OS, OS types, OS evolution, OS characteristics, and OS functions
• Module also covers how to interact with an OS, as well as UNIX, Linux, Ubuntu, and Windows architectures
• Module also covers interfaces, subsystems, GUIs, command lines, batch files, and the Windows and UNIX interfaces.
• Module also covers processes, programs, states, concurrency, interprocess communication, CPU scheduling, and threads.
• Scheduling policies are covered, including pre-emptive and non-pre-emptive, deadlock, real-time scheduling, and examples.
• Module also covers files, operations, directories, pathnames, file types, sharing, links, attributes, disk structures, and file system examples like MS-DOS, Windows, and UNIX.
• Module covers memory hierarchy, address spaces, static/dynamic memory, allocation, swapping, relocation, paging, segmentation, and virtual memory.
• Also focuses on security threats, attackers, malware, defenses, authentication, and controlling resource access
• Principles of I/O hardware, device drivers, buffering, spooling, and driver structure are also covered.

Module Assessment Breakdown

• The Coursework In-Class Test will account for 50% of the overall grade
• The End of Semester Exam covers remaining 50%

Lecture Agenda

• Introduction to Operating Systems (OS)
• Typical OS characteristics
• Operating System Responsibilities
• Historical background of OSs
• Overview of Windows and Unix
• Brief overview of Windows NT and Unix
• Structure of a typical OSs

What is an Operating System

• The computer is the sum of computer software and computer hardware
• Computer software = System Software + Application Software.
• System software is a general programming environment for programmers
• System software interfaces hardware with application software
• Application software consists of programs that perform tasks
• Operating System is the most important piece of system software

Computer Hardware

• The comprehensive term for the physical parts of a computer
• This includes CPU, Memory, Disks, Motherboard, Input Devices (mouse, keyboard) Output Devices (printer, monitor), etc.

System Software

• Provides a general programming environment in which programmers can create specific applications to suit their needs
• Acts as an interface between the hardware of the computer and the application software that users need to run on the computer.

Application Software

• Collection of programs used for performing different tasks
• Examples include spreadsheets, database systems, desktop publishing systems, program development software, and games.
• Programs designed to solve specific user problems

Operating Systems

• Software program that manages the available hardware resources on a computer
• It acts as an interface between a user of a computer and the computer hardware

Operating System Responsibilities

• The OS performs basic tasks such as:
  • Recognizing input from the keyboard.
  • Sending output to the display screen.
  • Keeping track of files and directories on the disk.
  • Controlling peripheral devices (e.g. disk drives and printers).
• Ensures different programs and users do not interfere with each other when running things simultaneously
• Provides the software platform on which other programs can run

Operating Systems Characteristics

• Concurrency: OS should be able to activate multiple apps. at the same time
• Sharing: Resources shared between running processes
• Long Term Storage: OS should be able to store data across reboots
• Effeciency
• Reliability
• Maintainability
• Small size

History of Operating Systems

• In the second generation era computers (1955-1965), mainframes were expensive and operated by professionals in air-conditioned rooms
• The logically monitor program helped monitor behavior and load other programs
• The logically monitor is the ancestor to today's operating systems
• In the third generation of computers(1965-1980), IBM introduced the System/360 called the ‘family’ of computers, which were software-compatible
• IBM also included a single OS called OS/360
• Techniques like Multiprogramming and spooling were introduced to increase operability
• Timesharing was introduced as a variant of multiprogramming, where each user had access online rather than offline
• The Unix OS was developed in the 1970s at AT&T Bell Laboratories
• The fourth generation of computers (1980-Present) featured the introduction of the Personal Computer.
• Early 1980s saw IBM design the IBM PC and then looking around for an OS to run on it
• Bill Gates bought DOS (Disk Operating System) from a company and modified it to create what is now known as MS-DOS (Microsoft Disk Operating System)
• Windows 95 was the first freestanding version of Windows and used MS-DOS only for booting
• Windows NT was introduced as Another Microsoft Operating System

Choosing an OS

• Existing Hardware:
  • It is pertinent to know if you want to upgrade or keep existing hardware
• Software:
  • Check for compatibility of required software
• Your Knowledge level:
  • Understanding the learning curve for a new OS is important
• Budget:
  • OS costs vary widely so choosing one in a budget is key
• Security:
  • Should provide password protection and have security protocols
• Reliability:
  • How costly is the effect of a crash on your business?
  • Does the OS have crash tolerance?
• Responsiveness:
  • How much does processing speed matter?
  • How fast is OS performance and what are the hardware demands?
• User interface that suits your tastes
  • Is it worthwhile to learn new operating paradigms?
• New software requirements
  • Does the software require a specific operating system platform?
  • Does the platform improve or not improve the performance of the software?
• Will choosing this OS improve or harm knowledge sharing vs what's already present in organization?

OS Example - Desktop

• Windows:
  • Windows 95, 98, ME (Microsoft)
  • Windows NT (Microsoft) (1993)
    • Windows 2000, Windows XP, Windows Vista (Jan 2007), Windows 7 (Oct 2009), Windows 10 (July 2015)
• Mac OS (Apple)
• Solaris (Sun)
• Unix (Free Software Foundation)
  • Linux (a PC Version), RedHat, Ubuntu

Windows NT (Server)

• Main releases include
  • Windows NT 3.1
  • Windows NT Server 3.5
  • Windows NT Server 3.51
  • Windows NT 4.0 Server
  • Windows 2000 Server
• Support for a wide variety of new Plug and Play hardware (e.g. wireless products, USB devices, infrared devices, etc.)
  • Windows Server 2003
  • Windows Server 2003 R2
  • Windows Server 2008
  • Windows Server 2008 R2
  • Windows Server 2012
  • Windows Server 2012 R2
  • Windows Server 2016
  • Windows Server 2019
  • Windows Server 2022
  • Windows Server 2025 (soon)

Windows NT (Main Characteristics)

• Is a 32-bit or 64-bit Operating System
• It allows resources to be assigned to a different process at will, instead of waiting for a process to complete
• Supports Concurrent execution of two or more tasks
• Includes Security support, Compatibility with other OS's, Friendly GUI Interfaces, Stability, Reliability, Hierarchical File store:
• Support for connecting to a network of computers and common server systems

Windows Server, "what 32-bit means"

• The processor design & address bandwidth determine how much memory the cpu can access
• Address bus of ‘x’ width can have 2^x memory spaces
  • E.g.: 16 bit has 2^16 or 65,536 memory locations or 65Kb
• Modern 32 byte bus could have 2^32 - or 4 GB max space

Windows Server

• There are 2 interfaces you can use, The GUI (graphic user interface) and CLI (command line interface)

• GUI:

  • is more User friendly
  • Easy to use keyboard or mouse
  • Can run multiple apps in parallel

• CLI:

  • Skilled and well-trained users can use interface
  • Commands can be executed sequentially
  • May be faster with GUI to execute certain tasks

Unix Heritage

• Originally designed as a fun project at AT&T Bell Labs. in the 1960's
• Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas Mcllroy, and Joe Ossanna are it's developers
• Thompson's 'Space Travel' game - tested the boundaries of what computer could do at the time.
• Re-written in C in 1973 for speed and portability
• Designed to be command line system
• The Free Software Foundation was created in 1984
• It aims to reproduce all UNIX in a version free of licensing

Unix-like Operating Systems

• Linux: Open-source Unix-like; used by Ubuntu, Fedora, Debian, and CentOS.
• FreeBSD: Descended from Berkeley Software Distribution (BSD).
• OpenBSD: Security-focused, derived from FreeBSD.
• NetBSD: Known for portability across hardware architectures.
• macOS: Apple OS, from NeXTSTEP and BSD. Core is called Darwin.
• Solaris: From Sun Microsystems, owned by Oracle.
• AIX: Developed by IBM for its Power Systems.
• HP-UX: Developer by Hewlett Packard.

Unix Main Characteristics

• Source code available for public use and modification, fostering collaboration and tailoring.
• OS supports multi-tasking, which means that more than one application can run at a time
• Supports operations from more than one user simultaneously
• Portability: C language allows operation on diverse hardware by separating what is hardware dependent from what isnt.
• Supports internet connections.
• Supports network applications to be run (e.g., web browsing application).
• The OS provides tools and utilities that are simple and powerful
• OS can run bigger programs than RAM capacity shows!

Operating System Structure

• Operating System Structure from outermost to innermost:
  • User Interface, Security and Protection, Resource Allocation, File Management, Input/Output, Memory Mgt, System Nucleus, Hardware
• Structure is layered, where each layer provides functions based on the services within it.