Lesson 1 — Beginner

CS Fundamentals: MNC ka pehla filter

Har MNC interview mein CS Fundamentals ka round hota hai. Ye tumhara pehla filter hai — OS, DBMS, Networking. Clear karo toh aage badho.

⏱ 12 min• Beginner• No prerequisites

CS Fundamentals kyun important hai?

WHAT

CS Fundamentals mein Operating Systems (OS), Database Management Systems (DBMS), aur Computer Networking (CN) aata hai. Ye 3 subjects har technical interview mein poochte jaate hain — chahe tum fresher ho ya experienced.

WHEN

Interview ka first round — phone screen ya onsite. DSA ke saath-saath ye subjects bhi poochte hain. Amazon, Google, Microsoft — sab mein ye mandatory hai. Bina ye clear kiye, aage nahi badh paoge.

WHERE

Technical interviews, phone screens, coding rounds — har jagah. "Mutex kya hai?" "ACID properties batao" "OSI model samjhao" — ye sab common questions hain.

Mental Model: CS Fundamentals jaise building ki foundation hai. DSA hai building ka structure, System Design hai architecture. Bina foundation ke building nahi tikti. Tumhe concepts clear hone chahiye — ratna nahi, samajhna hai.

Teen Subjects ka Overview

# 1. Operating Systems (OS)
? Computer kaise kaam karta hai internally
? Processes, Threads, Memory Management
? CPU Scheduling, Deadlocks, File Systems
? Real examples: Linux kernel, Windows scheduler

# Key Topics:
- Process vs Thread
- Context Switching
- Virtual Memory, Paging, Segmentation
- CPU Scheduling Algorithms
- Deadlock: Prevention, Avoidance, Detection
- Mutex, Semaphore, Monitors

# 2. Database Management Systems (DBMS)
? Data kaise store, retrieve, manage hota hai
? SQL, Transactions, Indexing, Normalization
? Concurrency Control, ACID properties
? Real examples: MySQL, PostgreSQL, MongoDB

# Key Topics:
- SQL queries (JOINs, GROUP BY, subqueries)
- B-Tree Indexing
- ACID Properties
- Normalization (1NF, 2NF, 3NF, BCNF)
- Locks, Deadlock in DBMS
- Transactions, Isolation Levels

# 3. Computer Networking (CN)
? Computers kaise communicate karte hain
? OSI Model, TCP/IP, HTTP, DNS
? Routing, Protocols, Security
? Real examples: Internet, WiFi, HTTPS

# Key Topics:
- OSI 7 Layers
- TCP vs UDP
- HTTP Methods (GET, POST, PUT, DELETE)
- DNS Resolution
- HTTPS, SSL/TLS
- IP Addressing, Subnetting

Interview Strategy

# Preparation Timeline:

Week 1: Operating Systems
? Day 1-2: Process, Thread, Context Switch
? Day 3-4: Memory Management (Virtual Memory, Paging)
? Day 5: CPU Scheduling
? Day 6: Deadlocks
? Day 7: Revision + Practice Questions

Week 2: DBMS
? Day 1-2: SQL (JOINs, Queries)
? Day 3: B-Tree Indexing
? Day 4: ACID, Transactions
? Day 5: Normalization
? Day 6: Concurrency (Locks, Deadlock)
? Day 7: Revision + Practice Questions

Week 3: Computer Networking
? Day 1-2: OSI Model, TCP/IP
? Day 3: HTTP, HTTPS
? Day 4: DNS, IP Addressing
? Day 5: Routing basics
? Day 6: Security (SSL, TLS)
? Day 7: Revision + Practice Questions

Week 4: Mixed Practice
? Top 50 CS questions practice
? Mock interviews
? Revision of weak areas

# Daily Strategy:
? 2 hours theory padho
? 1 hour questions solve karo
? Notes banao — key points
? Revision karo kal ke liye

Interview Tips

# CS Interview Format:
? 30-45 minutes per subject
? 5-8 questions expected
? Mix of theory + practical

# Common Questions:
OS: "Process aur Thread mein kya difference hai?"
DBMS: "ACID properties explain karo"
CN: "TCP aur UDP mein kya difference hai?"

# How to Answer:
1. Definition do (1 line)
2. Example do (real-world)
3. Comparison (vs alternatives)
4. Use case (kab use karte hain)

# Example Answer:
"Process ek independent program hai jo apna
memory space rakhta hai. Jaise Chrome ka har
tab ek naya process hai. Thread process ke
andar ka lightweight unit hai — same memory
share karta hai. Browser mein har tab ek thread hai."

# Tips:
? Concepts clear karo, ratna mat
? Real-world examples do
? Diagrams banao (OSI model, memory layout)
? "Pata nahi" bolo agar nahi aata — but try karo
? Follow-up questions ke liye ready raho

Exercise

Question: CS Fundamentals mein kitne core subjects hain jo har MNC interview mein aate hain? (3 subjects batao)

Question: CS Fundamentals interview round interview process mein kya kehlaata hai? (1-2 words)

Common mistakes

Sirf DSA karna: DSA important hai but CS Fundamentals bhi utna hi important hai. Dono karo.
Ratna approach: Concepts samjho, ratna mat. Interview mein conceptual questions poochte hain.
Examples na dena: Theoretical answer ke saath real-world example do — interviewer impress hota hai.
Ek subject skip karna: OS, DBMS, CN — teeno important hain. Koi bhi skip mat karo.

Lesson complete?

CS Fundamentals overview samajh aa gaya? Ab Operating Systems ke Processes vs Threads seekhte hain — pehla core topic.