Notes, summaries, assignments, exams, and problems for Computers

What is a Computer Network?

A computer network connects two or more computing devices, such as computers, servers, routers, or switches, through wired or wireless communication channels. This enables efficient sharing of data, resources, and applications.

The primary purpose of a computer network is to facilitate communication and resource sharing among users and devices, whether within a small area like a home or office, or across large geographical regions like the internet.

Advantages of Computer Networks

1. Resource Sharing: Devices like printers, scanners, and internet connections can be shared across the network, reducing hardware costs.
2. Data Sharing: Users can easily share files and data in real-time, improving collaboration and efficiency.
3. Centralized

Types of Operating Systems

This section details various types of operating systems, each designed to meet specific needs and requirements.

Real-Time Operating System (RTOS)

• Designed for applications that require predictable and fast responses to events.
• Guarantees a response within a specified time frame.
• Examples: Industrial control systems, medical devices, automotive systems, aerospace systems.

Characteristics of RTOS

• Predictable response times
• High reliability
• Efficient resource utilization

Batch Processing Operating System

• Executes a series of jobs (programs) in a batch, without user interaction.
• Jobs are collected, processed, and output is generated.
• Examples: Mainframe systems, scientific simulations, data processing.

Characteristics of Batch Processing

Object-Oriented Programming (OOP) Fundamentals

Object-oriented programming (OOP) is a computer programming model that uses objects to represent and manipulate data.

OOP is well-suited for large, complex, and frequently updated software. Some of the main features of OOP include:

• Classes: User-defined data types that serve as a blueprint for individual objects, attributes, and methods.
• Objects: Instances of a class that are created with specific data.
• Methods: Functions that objects can perform.
• Attributes: Represent the state of an object.
• Abstraction: Exposes only the essential information of an object to the user.
• Polymorphism: Adds different meanings to a single component.
• Inheritance: Allows a class to inherit the properties and methods of another

Node.js Fundamentals

Understanding Node.js Modules

Modules in Node.js are reusable pieces of code that can be exported from one file and imported into another. Each file in Node.js is considered a module, operating within its own scope. Modules help organize code into separate files for better maintainability and reusability.

Types of Node.js Modules:

1. Core Modules: Built-in modules provided by Node.js, pre-installed and ready to use.
2. Local Modules: Custom modules created by developers for specific application logic.
3. Third-party Modules: Modules installed via npm (Node Package Manager), extending Node.js functionality.

Key Built-in Node.js Core Modules

Core modules are essential, pre-installed components of Node.js. You can use them directly in your... Continue reading "Core Web Development Concepts: Node.js, Express, React, Redux, MongoDB" »

Essential Network Commands

• tracert Utility

  • Displays the route taken to a destination.
  • Identifies where delays or packet loss occur in the network path.
  • Syntax: tracert <destination>

• netstat Utility

  • Displays active TCP connections and other network statistics.
  • Useful for monitoring network connections.
  • Syntax: netstat

• ipconfig Utility

  • Displays IP configuration information.
  • Can be used to release and renew IP addresses.
  • Syntax:
    • Display configuration: ipconfig
    • Release IP address: ipconfig /release
    • Renew IP address: ipconfig /renew

• nslookup Utility

  • Queries DNS to obtain domain name or IP address mappings.
  • Syntax: nslookup <domain>

• ping Utility

  • Tests connectivity between two devices by sending ICMP echo requests.
  • Syntax: ping <destination>
  • Common Options:

Memory Models in Operating Systems

• Model A (MS-DOS):
  • Structure: Large user space at the top, small RAM at the bottom.
  • Performance: Fast execution, long boot time.
  • Protection: No protection.
• Model B:
  • Structure: Small ROM at the top, small user space at the bottom.
  • Performance: Protected OS but slow (the entire OS must be read).
  • Flexibility: Not flexible.
• Model C (Windows 11):
  • Structure: Select drivers at the top, large user space in the middle, RAM at the bottom.
  • Performance: Fast and secure (key drivers stored in ROM).

Memory Protection and Management

Core Memory Management Issues

• Relocation Problem: Without memory abstraction, loading multiple programs causes incorrect memory addresses.
• Base and Limit Registers:
  • Base: Value added to addresses to find

Understanding Node.js Modules & Core Functionality

In Node.js, modules are fundamental. They represent reusable blocks of code that can be exported from one file and imported into another, promoting a modular and organized application structure. Node.js features a built-in module system, allowing developers to utilize core modules, create custom modules, or integrate third-party modules.

Core Modules in Node.js

Core modules are pre-packaged with Node.js, offering essential functionalities for common tasks like file system operations, HTTP request handling, and path manipulation.

Some commonly used core modules in Node.js are:

• fs (File System): For interacting with the file system.
• http (HTTP): For creating HTTP servers and clients.
• path (Path)

IoT Protocols

Link Layer Protocols

• 802.3 Ethernet Standards

  A collection of wired Ethernet standards that provide data rates from 10 Mb/s to 40 gigabits per second. The shared medium in Ethernet can be a coaxial cable, twisted-pair wire, or optical fiber. This shared medium carries communication for all devices on the network.

• 802.11 Wi-Fi Standards

  A collection of wireless Local Area Network (WLAN) communication standards.

Network/Internet Layer

• Responsible for sending IP datagrams from the source network to the destination network.
• Handles host addressing and packet routing based on IPv4 or IPv6.
• Datagrams contain a source and destination address, which are used to route them from the source to the destination across multiple networks.
• IPv4 uses 32-

Elliptic Curve Cryptography (ECC) in Blockchain

Elliptic Curve Cryptography (ECC) is a public-key cryptography technique based on the mathematics of elliptic curves over finite fields. It is widely used in blockchain systems such as Bitcoin and Ethereum for generating secure public-private key pairs and digital signatures. The main advantage of ECC is that it provides high security with smaller key sizes, making it faster and more efficient.

The Mathematical Equation of ECC

The general equation of an elliptic curve is:

y2 = x3 + ax + b

• a and b are constants that define the shape of the curve.
• The curve is defined over a finite field Fₚ (where p is a prime number) for cryptographic applications.
• To be a valid elliptic curve, it must satisfy the condition:

Operating System Memory Management Fundamentals

The Operating System (OS) is responsible for crucial memory decisions: determining which programs reside in memory, where they are placed, how memory is protected, and what actions to take when memory resources are exhausted.

Parkinson's Law Applied to Computing

Parkinson’s Law states that programs expand to fill the memory available to hold them.

Models for Organizing Memory

Three primary models exist for structuring memory:

• Model A (User on Top, RAM on Bottom):
  • Pros: Fast execution.
  • Cons: No protection (e.g., used in MS-DOS).
• Model B (ROM on Top, User on Bottom):
  • Pros: OS protected.
  • Cons: Slow and not flexible.
• Model C (Drivers at Top, User in Middle, RAM at Bottom):
  • Pros: Fast and secure.
  • Cons: Complex