Operating Systems Overview

Examples of Operating Systems

• Desktop/Laptop Operating Systems: Windows, Mac OS, UNIX, Linux
• TV Operating Systems: Samsung Smart TV (Tizen), VIZIO (SmartCast OS), Roku and Roku TVs (Roku OS)
• Smartphone Operating Systems: Apple iOS, BlackBerry OS, Android
• Internet of Things (IoT) Operating Systems: Contiki, Amazon FreeRTOS, Embedded Linux, RIOT, TinyOS, Windows 10 IoT

Functions of Operating Systems

• Oversee computer operations
• Store and retrieve files
• Provide a user interface to execute programs
• Coordinate the execution of programs

History of Operating Systems

• Batch Processing: jobs executed in a queue
• Interactive Processing: real-time execution
• Time-Sharing: Multiple users sharing one machine
• Multitasking: One user running multiple tasks
• Multiprocessor Machines: Load balancing across multiple processors
• Embedded Systems: Operating systems designed for specific devices

Operating System Architecture

• Application Software: Performs specific tasks for users, such as productivity software, games, and development tools.
• System Software: Provides the infrastructure for application software, includes the operating system and utility software.

Components of an Operating System

• User Interface: Communicates with users, can be text-based (shell) or graphical (GUI).
• Kernel: Performs the basic required functions of the operating system.
• File Manager: Manages files and directories.
• Device Drivers: Provides communication with hardware devices.
• Memory Manager: Manages the allocation and use of computer memory.
• Scheduler and Dispatcher: Manages the scheduling and execution of processes and tasks.

Loading Software and Managing Memory

• The computer starts by booting a loader program in memory.
• The boot loader then loads the operating system from mass storage into memory.
• This process is called booting and transfers control to the operating system.

Types of Networks

• Personal Area Network (PAN): Short-range network, often used for devices like phones, watches, and headphones.
• Local Area Network (LAN): Network within a building or campus.
• Metropolitan Area Network (MAN): Network spanning a city or community.
• Wide Area Network (WAN): Covers a large geographical area, often used for connecting different LANs or MANs.

Network Ownership

• Closed (Proprietary) Network: Proprietary network with restricted access.
• Open (Public) Network: Uses open standards and provides services on an equal basis.

Network Topology

• Bus Topology: All devices share a single cable, example is Ethernet.
• Star Topology: All devices connect to a central access point.

Network Protocols

• Protocol: Rules governing network activities, enabling communication between diverse devices.
• Data transmission control and coordination between network nodes.

Transmission Protocols

• CSMA/CD (Carrier Sense, Multiple Access/Collision Detection): Used in bus networks to detect collisions between data transmissions and avoid data loss.
• CSMA/CA (Carrier Sense, Multiple Access/Collision Avoidance): Used in star networks to prevent collisions by requiring devices to request permission before transmitting data.

Combining Networks

• Repeater: Amplifies and forwards signals between two bus networks.
• Bridge: Connects two bus networks, only forwarding data destined for devices on the other network.
• Switch: Similar to a bridge, but connects multiple bus networks.
• Router: Connects two incompatible networks, forming a network of networks, also known as an internet.

An Internet, Not the Internet

• Defines a network of interconnected networks, regardless of size or geographical scope.

Process Communication

• Interprocess Communication (IPC): Enables communication between network nodes to coordinate actions and perform tasks.
• Client-Server: A model where multiple clients make requests to a single server, which processes and fulfills those requests.
• Peer-to-Peer (P2P): A model where two processes communicate as equals, typically on a temporary basis.

Distributed Systems

• Distributed Systems: Systems with units executing as processes on different computers.
• Cluster Computing: Independent computers working together as a single, larger
• Grid Computing: Millions of PCs working together on a complex problem.
• Cloud Computing: A model where services are provided, hiding the underlying infrastructure details.

The Internet

• The Internet: A global network of interconnected networks.
• Original Goal: DARPA initiative to create a resilient communication system, linking diverse networks and resistant to local disasters.

Internet Architecture

• Tier 1 ISPs: Form the backbone of the Internet, providing high-bandwidth connections between networks.
• Tier 2 ISPs: Regional Internet service providers.
• Tier 3 ISPs: Access providers connecting users to the Internet.

Addresses on the Internet

• IP Address: A unique identifier for each device connected to the Internet, usually represented in dotted decimal notation (e.g., 192.168.10.1).
• ICANN (Internet Corporation for Assigned Names and Numbers): Responsible for allocating IP address blocks to ISPs.

Domains and Domain Names

• Registrars: Companies authorized to register domain names on behalf of organizations.
• Mnemonic Name: A human-readable name for a website or service, often based on the organization or entity it represents (e.g., monroecc.edu, youtube.com).
• Top-Level Domains (TLDs): Suffixes identifying the type or origin of a domain, such as .com, .net, .org, .edu, .gov, .au, .uk, etc.
• New TLDs: Introduced to expand the number of domain options, include .biz, .museum, .tech, .info, .news, .mobi, etc.
• Subdomains: Portions of a domain that further organize content, such as maps.google.com.
• Domain Name System (DNS): A system of name servers that translate domain names into IP addresses.

Early Internet Applications

• NNTP (Network News Transfer Protocol): Protocol used for transmitting newsgroup articles.
• FTP (File Transfer Protocol): Protocol for transferring files between computers.
• Telnet and SSH (Secure Shell): Protocols used for establishing secure remote connections.
• HTTP (Hypertext Transfer Protocol): Protocol used for transferring web content.
• Email: Electronic mail, using SMTP (Simple Mail Transfer Protocol) for sending and POP3 and IMAP for accessing.

More Recent Applications

• VoIP (Voice over IP): Transmitting voice calls over the Internet.
• Internet Multimedia Streaming: Transferring multimedia content over the Internet, including:
  • Unicast: Transmissions from one sender to one receiver.
  • Multicast: Transmissions from one sender to multiple receivers simultaneously.
  • On-demand streaming: Content available to users whenever they wish.
  • Content Delivery Networks (CDNs): Networks of servers distributing content closer to users for improved performance.
  • Anycast: Transmissions sent to a group of servers, with the closest server responding.
• World-Wide Web: A system that combines Internet technology with linked documents (hypertext), making information more accessible.
  • Hypertext: Text containing embedded links to other documents
  • Web Browsers: Software applications used to view and interact with web content.
  • Web Servers: Provide access to web documents.
  • URLs (Uniform Resource Locators): Addresses used to identify and locate resources on the web.
  • HTTP (HTTPS) - Protocol used to transfer web documents.

Anatomy of a URL

• Mnemonic name of the host: The domain name (e.g., google.com).
• Protocol required to access the document: The scheme, often 'http' (e.g., http://).
• Directory path: Indicates the location of the document within the host's file system.
• Document name: The name of the specific file being accessed (e.g., index.html).

Hypertext Markup Language (HTML)

• HTML (Hypertext Markup Language): A language used to create web pages, using tags to structure and format content.
• HTML tags instruct web browsers on how to present the content.
• Commonly used tags:
  • <h1> to </h1>: Heading level 1.
  • <p> to </p>: Paragraph.
  • <a href="URL">: Hyperlink to another URL.
  • <img src="URL">: Inser an image from a specified URL.

Client-Side vs. Server-Side

• Client-Side Activities (Browser): Performed by the user's browser.
  • Front End: Handles user input, visual presentation, and interaction.
  • Languages include: JavaScript, CSS, jQuery.
• Server-Side Activities (Web Server): Performed by the server hosting the website.
  • Back End: Processes user input, handles transactions, and performs computations.
  • Languages include: PHP, Python/Django, ASP.NET.

Internet Protocols

• Internet Protocols: Establish rules for data transfer across the Internet.
• Implemented on all interconnected computers.
• Hierarchy of Layers: - Application Layer - Transport Layer - Network Layer - Link Layer

TCP/IP Protocol Suite

• Application Layer: Responsible for providing services for applications, such as email, web browsing, and file transfer protocols.
• Transport Layer: Manages the transmission of data between applications, including TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
• Network Layer: Handles routing and addressing, using IP (Internet Protocol).
  • IPv4: the older 32-bit IP addressing scheme (e.g., 192.168.10.1).
  • IPv6: The newer 128-bit IP addressing scheme, providing a much larger address space (e.g., 0:0:0:0:0:ffff:c0a8:0a01).

Client-Server Programming:

• Describes how applications communicate with each other.
• The client makes a request to the server (e.g. accessing a website), and the server processes the request and sends back a response.
• The relationship between the client and server can be one-to-one, one-to-many, or many-to-many.