Operating Systems and Network Fundamentals

Posted on Jan 13, 2025 in Computers

Operating Systems

An Operating System (OS) is a set of software algorithms and routines intended to allocate resources to processes and provide a user-friendly environment that hides the hardware details.

Types of Operating Systems

For the Number of Users

  • Monouser (e.g., DOS)
  • Multiuser

By the Number of Concurrent Processes (Tasks)

  • Single-tasking or Uniprocessor (e.g., DOS)
  • Multitasking or Multiprocessing
  • Multitasking Time-Shared (the larger the higher priority, the more runtime the process will have)
  • Multiprocessing (2 CPUs or more)

For the Processing Mode

  • As Equals: They provide and request services without distinction.
  • Host
  • Client/Server

OS Functions

  • Shell
  • Device Management (interrupts) IRQ
  • Concurrent Processes (effectiveness)

Users and Groups

From this console, you can create users and groups. Users can belong to groups and inherit their characteristics. For each user and group, you can set a number of options, such as whether they can change the password, if it’s enabled, and which permissions they have. You can force them to use passwords that have to be changed within certain deadlines and other aspects of their profiles. Each user and group has a unique ID that is not deleted. For example, if a user named Jorge is created, deleted, and recreated, it will not be the same, nor will it automatically have Jorge’s previous characteristics. This ID is a long string that serves as a unique and unrepeatable identification code.

Network Definition

A network is a set of data processing equipment interconnected to share data.

Network Types

By Size

  • LAN: Local Area Network
  • MAN: Metropolitan Area Network
  • WAN: Wide Area Network

By Mode of Operation

  • P2P: As equals. (e.g., Windows networks)
  • Host Networks: Centralized and connected to dumb terminals
  • Client/Server Networks: Servers that provide clients with resources and capabilities
  • 3-Tier Architecture: Data, applications, and Web Client

By Topology

  • Physical (physical layout)
  • Logical (data flow)
Physical Bus
  • BNC connectors, thin coaxial cable
  • What a team transmits is received by all (broadcast), but only processed by the receiver.
  • Competition for the physical environment => collisions
  • Logical bus topology
  • Physical and logical bus => Ethernet (IEEE 802.3)
Examples
Physical and Logical Ring
  • Transmissions through the token or control (shift transmissions). The team is responsible for maintaining the list of active equipment.
  • It is an IBM patent.
  • Problem: loss of token. Solution: create a new token. New problem: duplication of the token.
Physical Star Topology
  • It is less vulnerable than previous topologies, but as a centralized scheme, if the interconnection element (IE) fails, it creates a network bottleneck.
  • The logical topology depends on the interconnection element (IE):
    • HUB: Bus logic level devices
    • MAU (Multiple Access Unit):
      • Token “shift” logic ring (token ring networks)
      • Competition for the token: logic bus (token bus networks)
    • Switch (database of connected computers: MAC address): Logic level bus ports, port-level collisions.
Hierarchical Physical Topology
  • Reproduces the hierarchy of the company.
Mesh Topology
  • All computers on the network are connected to each other, providing redundancy and/or alternative paths.