Inheritance in Object-Oriented Programming (OOP)
Inheritance is an OOP concept where a child (derived) class inherits properties and behaviors from a parent (base) class. It helps reuse existing code and represents real-world hierarchical relationships (like Animal → Dog).

Types of Inheritance

1) Single Inheritance
One child class inherits from one parent class.

Animal
  |
 Dog

Here, Dog inherits features (like eating, breathing) from Animal.

2) Multiple Inheritance
One child class inherits from more than one parent class.

Printer     Scanner
     \     /
      \   /
     AllInOne

Here, AllInOne inherits features of both Printer and Scanner.

3) Multilevel Inheritance
A class is derived from another derived class, forming a chain.

Vehicle
   |
  Car
   |
ElectricCar

Here, ElectricCar indirectly inherits features from Vehicle through Car.

Software Development Life Cycle (SDLC)
The Software Development Life Cycle (SDLC) is a structured process used to design, develop, test, deploy, and maintain software systems. It provides a systematic approach to building high-quality software that meets user requirements, stays within budget, and is delivered on time.

Main Phases of SDLC

1) Requirement Analysis
In this phase, user needs and system requirements are collected and analyzed to understand what the software should do.

2) System Design
Based on the requirements, the overall system architecture, database design, and technical specifications are prepared.

3) Implementation (Coding)
The actual software is developed by writing code according to the design specifications.

4) Testing
The software is tested to identify and fix bugs and ensure it works correctly and meets user expectations.

5) Deployment
After successful testing, the software is released and deployed in a real user environment.

6) Maintenance
Once deployed, the software is maintained through updates, bug fixes, and enhancements based on user feedback.

IP Addressing and Routing with OSPF
IP addressing provides a unique logical address to every device in a network, which allows packets to be identified and routed to the correct destination. Routing is the process of selecting the best path for these packets to travel across interconnected networks.

Role of OSPF at the Network Layer
Open Shortest Path First (OSPF) is a link-state routing protocol used at the network layer. Each router running OSPF maintains a complete map of the network topology using IP addresses and link information.

How Packet Delivery Works Using OSPF
• Routers exchange link-state advertisements (LSAs) containing information about their networks and IP subnets.
• Each router builds a link-state database representing the entire network.
• OSPF uses the Dijkstra shortest path algorithm to calculate the best path to every destination IP network based on cost (bandwidth).
• The routing table is updated with the shortest paths.
• When a packet arrives, the router checks the destination IP address and forwards the packet to the next-hop router based on the routing table.

Result
Using IP addressing for identification and OSPF for intelligent routing, packets are delivered efficiently, reliably, and dynamically across large networks, even when network changes occur.

Universal Gate
A Universal Gate is a logic gate that can be used to implement any Boolean function (i.e., any logic circuit). If we can build the basic gates NOT, AND, and OR using only one type of gate, then that gate is called a universal gate.

Proof: NAND is a Universal Gate
To prove NAND is universal, we show that we can construct NOT, AND, and OR using only NAND gates.

Since we can build NOT, AND, and OR using only NAND gates, we can build any Boolean expression. Therefore, the NAND gate is a Universal Gate.

Version Control (Git)
Version Control is a system that helps developers track changes in source code over time. Git is a popular version control system that allows multiple developers to work on the same project, manage different versions of code, and revert to previous states when needed.

Difference between Committing and Pushing Code
Committing Code
Committing means saving changes to the local repository. It records a snapshot of the code with a message describing what was changed. The changes are stored only on the developer’s local machine.

Pushing Code
Pushing means sending committed changes from the local repository to a remote repository (such as GitHub or GitLab). This makes the changes available to other team members.

Key Difference
Committing saves changes locally, while pushing uploads those committed changes to a remote server.