✅ Software Design Principles (SOLID, DRY, KISS, etc.)

Software Design Principles ek set of guidelines hote hain jo developers ko clean, maintainable aur scalable code likhne me help karte hain. Agar ye follow kiye jayein to software zyada reliable, flexible aur bug-free banta hai.

🔹 1. SOLID Principles

SOLID ek acronym hai jo 5 important OOP (Object-Oriented Programming) design principles ko represent karta hai.

1️⃣ S – Single Responsibility Principle (SRP)

Har class/function ka sirf ek hi responsibility hona chahiye.
Example: Ek class jo "User Authentication" handle kare, wo "Email Notifications" bhi na kare.

2️⃣ O – Open/Closed Principle (OCP)

Code extension ke liye open hona chahiye but modification ke liye closed.
Matlab naye features add karna easy ho but purane code ko bar-bar modify na karna pade.

3️⃣ L – Liskov Substitution Principle (LSP)

Derived (child) class ko base (parent) class ke jagah use kar sakein without breaking functionality.
Example: Agar Bird class me fly() method hai, to Penguin (jo fly nahi karta) uska child nahi hona chahiye.

4️⃣ I – Interface Segregation Principle (ISP)

Clients ko unnecessary methods implement karne ko force nahi karna chahiye.
Example: Agar "Printer" interface hai, to scan(), fax() methods alag interface me honi chahiye.

5️⃣ D – Dependency Inversion Principle (DIP)

High-level modules ko low-level modules pe directly depend nahi karna chahiye.
Dono ko abstraction (interfaces) pe depend karna chahiye.

🔹 2. DRY Principle (Don’t Repeat Yourself)

Repeated code likhne se bacho.
Reusable functions, methods aur modules banao.
Example: Agar "Calculate Tax" 3 jagah use ho raha hai to ek common function banao instead of copy-paste.

🔹 3. KISS Principle (Keep It Simple, Stupid)

Code ko unnecessarily complex mat banao.
Simple aur easy-to-understand solutions likho.
Example: Ek loop me hi problem solve ho rahi hai to recursion ka overuse na karo.

🔹 4. YAGNI Principle (You Aren’t Gonna Need It)

Future me kaam aayega ye soch kar unnecessary features mat banao.
Sirf wahi implement karo jo abhi requirement me hai.

🔹 5. High Cohesion & Low Coupling

High Cohesion: Related functionalities ek module/class me ho.
Low Coupling: Classes/modules ek dusre pe kam depend karein.

📊 Quick Summary Table

Principle	Full Form	Key Idea
SOLID	5 OOP principles	Clean & maintainable OOP design
DRY	Don’t Repeat Yourself	Avoid duplicate code
KISS	Keep It Simple, Stupid	Keep code simple & easy
YAGNI	You Aren’t Gonna Need It	Don’t add unnecessary features
Cohesion & Coupling	—	Related things together, minimize dependencies

🔹 Conclusion

Software Design Principles help developers write readable, reusable, testable, and scalable code. By following SOLID, DRY, KISS, and YAGNI, we can avoid spaghetti code and ensure that our software remains maintainable in the long run

software engineering