System Design & C++ Interview Preparation

A comprehensive resource for mastering System Design, Object-Oriented Programming (OOP), and C++ fundamentals for technical interviews.

🎯 Purpose

This repository is designed for:

• Interview preparation: Brush up on core concepts before technical rounds
• Learning system design: Step-by-step exploration of OOP principles
• Hands-on practice: Working code examples with detailed explanations
• Community resource: Anyone interested in strengthening their C++ and system design knowledge

📚 What's Inside

Current Topics

1. Access Modifiers

Complete guide to C++ access control mechanisms.

Covers:

• public, protected, private access specifiers
• Access vs Visibility (compilation phases)
• Friend mechanism (not an access specifier!)
• Protected access rules ("through what object?")
• Inheritance and access control
• Real-world examples and interview questions

Includes 4 Working Examples:

• example1/ - Basic access control & visibility
• example2/ - Protected "through what?" rule
• example3/ - Real-world: Bank account system
• example4/ - Inheritance types (public/protected/private)

📖 Read the full guide →

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2. Constructors & Destructors

Deep dive into object lifecycle management in C++.

Covers:

• Default, Parameterized, and Copy Constructors
• Shallow vs Deep Copy (critical for interviews!)
• Constructor Overloading
• Initialization Lists
• Destructors and RAII
• Rule of Three/Five
• Memory management with dynamic allocation
• Constructor calling rules and delegation

Includes Comprehensive Examples:

• 01_basic_constructor.cpp - Constructor fundamentals
• 02_parameterized_constructor.cpp - Controlled object creation
• 03_copy_constructor.cpp - Shallow vs Deep copy explained
• 04_constructor_overloading.cpp - Function overloading with 4 examples
• 05_initialization_list.cpp - Performance optimization
• 06_destructor_basics.cpp - Resource cleanup & RAII
• 07_constructor_destructor_order.cpp - Inheritance order & virtual destructors
• 08_special_cases.cpp - Explicit, Singleton, Factory patterns
• explicit_explained.cpp - explicit keyword deep dive
• cnstrs.cpp - Working example with Rule of Three

Status: Parts 1-8 complete ✅ CORE TOPICS DONE!

📖 Read the full guide →

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3. Inheritance

Complete guide to class hierarchies, polymorphism, and runtime dispatch in C++.

Covers:

• Inheritance basics (IS-A relationship)
• Types of inheritance (Single, Multiple, Multilevel, Hierarchical, Hybrid)
• Access control in inheritance (public, protected, private)
• Constructor/Destructor order in inheritance
• Function overriding and virtual functions
• Polymorphism and dynamic dispatch
• Abstract classes and pure virtual functions
• Diamond problem and virtual inheritance
• vptr/vtable mechanism deep dive (system-level understanding)
• Real-world examples (GUI toolkit, device drivers)
• Interview questions and best practices

Includes 10 Complete Examples:

• 01_inheritance_basics.cpp - Fundamental concepts
• 02_types_of_inheritance.cpp - All inheritance types
• 03_access_control.cpp - Access specifier rules
• 04_constructor_destructor_order.cpp - Object lifecycle
• 05_function_overriding.cpp - Method overriding
• 06_virtual_functions.cpp - Polymorphism basics
• 07_abstract_classes.cpp - Pure virtual functions
• 08_multiple_inheritance.cpp - Multiple base classes
• 09_real_world_example.cpp - GUI toolkit demo
• 10_private_inheritance_example.cpp - Advanced patterns
• vptr_vtable_visual.cpp - Internal mechanism visualization
• diamondprob.cpp - Diamond problem solution

Status: All 10 parts complete ✅ FULLY DOCUMENTED!

📖 Read the full guide →

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4. Concurrency Fundamentals

Systems programming perspective on processes, threads, and memory management.

Covers:

• Process vs Thread (fundamental differences)
• IPC mechanisms (pipes, shared memory, signals)
• Memory layouts (stack, heap, TLS, code/data segments)
• TCB/PCB in kernel memory
• Thread creation basics (pthread, std::thread)
• Process creation (fork, exec, wait)
• Virtual memory and address translation
• Context switching internals

Includes 12 Files:

• 00_single_thread_basics.cpp - Single thread timing demo
• 00_multi_thread_basics.cpp - Work splitting with atomic
• 01_process_vs_thread.cpp - fork vs thread comparison
• 02_ipc_internals.cpp - IPC mechanisms demo
• 02_ipc_pipe_basics.cpp - Pipe-based IPC basics
• 03_process_internals_deep_dive.md - TCB/PCB kernel details
• 04_thread_memory_layout.cpp - Stack/heap/TLS addresses
• 05_thread_vs_process_memory.md - Memory layout comparison
• 06_thread_create_basics.cpp - Simple thread syntax
• 07_process_create_basics.cpp - fork/exec/wait basics
• process_exp.cpp - Process creation experiment
• thread_experiments.cpp - Threading experiments playground

Status: Complete ✅ Systems perspective!

📖 Read the full guide →

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5. SOLID Principles ⭐ NEW!

Complete deep-dive into SOLID design principles with interview preparation materials.

Covers:

• Single Responsibility Principle - One class, one job
• Open/Closed Principle - Open for extension, closed for modification
• Liskov Substitution Principle - Subtypes must be substitutable
• Interface Segregation Principle - Small focused interfaces
• Dependency Inversion Principle - Depend on abstractions

Includes 6 Complete Examples:

• 01_srp_single_responsibility.cpp - Employee, User, Invoice systems
• 02_ocp_open_closed.cpp - Shapes, Payments, Notifications
• 03_lsp_liskov_substitution.cpp - Rectangle/Square, Birds, Accounts
• 04_isp_interface_segregation.cpp - Workers, Printers, Databases
• 05_dip_dependency_inversion.cpp - Dependency injection patterns
• 06_real_world_ecommerce.cpp - Complete e-commerce system with all SOLID

Interview Resources:

• CHEAT_SHEET.md - Quick reference for interviews
• INTERVIEW_GUIDE.md - Deep interview preparation
• STUDY_PLAN.md - 30-min to 1-week study plans
• Each file has BAD vs GOOD examples with explanations

Status: Complete ✅ Interview-ready!

📖 Read the full guide →

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6. OOP Relationships

Demonstrating all 4 OOP relationships with real-world Hospital Management System.

Covers:

• Inheritance (IS-A): Doctor/Patient inherit from Person
• Composition (Dies Together): Address in Person, MedicalRecord in Patient
• Aggregation (Independent): Department has Doctors
• Association (Temporary): Doctor examines Patient
• UML diagrams and arrow directions
• Memory management with raw pointers (pre-RAII)
• Interview-ready implementation

Project:

• hms.cpp - Complete Hospital Management System
  • Person base class with Address composition
  • Doctor and Patient inheritance
  • Department aggregation using pointers
  • examine() method for association
  • All 4 relationships demonstrated

Status: Complete ✅ Interview ready! Score: 9/10

Note: Using raw pointers for learning; will upgrade to smart_ptr after RAII topic.

📖 Read the full guide →

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6. Templates & Generics

Intro to writing reusable, type-safe code with templates.

Covers (so far):

• What templates are and why they matter (generic, type-safe reuse)
• Basic syntax for function and class templates

Includes 2 Examples:

• genrics_basic.cpp — function template addnum, class template Box<T>
• concepts_vs_sfinae.cpp — SFINAE constraints (C++17 compilable) with C++20 concepts documented as theory

📖 Read the guide → | ▶️ cd generics && make FILE=genrics_basic.cpp run

Next Up: constraints (concepts), specialization, perfect forwarding/move-aware templates

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7. Exception Handling

Practical exception-safety patterns with working samples.

Covers:

• try/catch basics and throwing functions
• Standard exception hierarchy and custom exceptions
• RAII stack unwinding
• Exception safety guarantees and noexcept
• Futures, nested exceptions, and error codes

Includes:

• 01_try_catch_basics.cpp through 10_error_code_vs_exception.cpp
• experiments.cpp - sandbox for patterns

📖 Read the guide →

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8. Synchronization

Thread-safety primitives and patterns.

Covers:

• Mutexes and shared mutexes
• Semaphores (native and C++20)
• Classic producer-consumer patterns
• Traffic counter example

Includes:

• sync_mutex.cpp, sync_shared_mutex.cpp
• semaphore_native.cpp, semaphore_cpp20.cpp
• producer_consumer.cpp, producer_consumer_advanced.cpp
• traffic_counter.cpp

📖 Read the guide →

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🏗️ Projects

Project suites demonstrating different C++ concepts and design patterns.

📖 View All Projects →

Quick Overview:

Project	Focus	Tech	Score
HMS	All 4 OOP Relationships	Raw Pointers	9/10
Payment Service	Polymorphism & RAII	Smart Pointers	9.5/10
System Programming (WIP)	Unix process/thread exercises	C/C++	WIP

Key Highlights:

• ✅ Interview-ready implementations with comprehensive documentation
• ✅ UML diagrams and design explanations
• ✅ Practice questions and talking points included
• ✅ No compiler warnings, clean code quality
• ✅ Makefile for easy compilation

📖 Explore Projects → | See Comparison Table →

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🗂️ Repository Structure

systemdesign/
├── README.md
├── acessmodifiers/
│   ├── README.md
│   ├── example1/
│   ├── example2/
│   ├── example3/
│   └── example4/
├── association/
│   ├── README.md
│   ├── PROBLEM_STATEMENT.md
│   ├── 01_association_basics.cpp ... 06_complete_example.cpp
│   ├── hms.cpp
│   └── makefile
├── concurrency/
│   ├── README.md
│   ├── 00_single_thread_basics.cpp ... 07_process_create_basics.cpp
│   ├── 02_ipc_pipe_basics.cpp
│   ├── process_exp.cpp
│   ├── thread_experiments.cpp
│   └── makefile
├── constructors-destructors/
│   ├── README.md
│   ├── 01_basic_constructor.cpp ... 08_special_cases.cpp
│   ├── explicit_explained.cpp
│   └── cnstrs.cpp
├── exceptionalhandling/
│   ├── README.md
│   ├── 01_try_catch_basics.cpp ... 10_error_code_vs_exception.cpp
│   ├── experiments.cpp
│   └── makefile
├── functorsExecutioners/
│   ├── README.md
│   ├── fp.cpp
│   ├── lambda_explanation.cpp
│   ├── lambda_explanation.md
│   └── makefile
├── generics/
│   ├── README.md
│   ├── genrics_basic.cpp
│   ├── concepts_vs_sfinae.cpp
│   └── makefile
├── inheritance/
│   ├── README.md
│   ├── 01_inheritance_basics.cpp ... 10_private_inheritance_example.cpp
│   ├── vptr_vtable_visual.cpp
│   └── diamondprob.cpp
├── projects/
│   ├── README.md
│   ├── HMS/
│   ├── paymentsystem/
│   └── systemprogramming/
└── synchronization/
    ├── README.md
    ├── sync_mutex.cpp, sync_shared_mutex.cpp
    ├── semaphore_native.cpp, semaphore_cpp20.cpp
    ├── producer_consumer.cpp, producer_consumer_advanced.cpp
    └── traffic_counter.cpp

Function Pointers, Functors, and Lambdas

Explore modern C++ callable objects, including:

• Function pointers (basic, callback, arrays, strategy)
• Lambdas (syntax, captures, STL,