Each module card shows: what you'll learn, key technologies, AND the most-asked interview questions from that topic. These modules aren't abstract CS theory — they're interview-focused, with every concept connected to questions companies actually ask.
How computers manage processes, memory, and storage — the internal workings every developer must understand. Process management (creation, states, scheduling — FCFS, SJF, Round Robin, MLFQ), threads (user vs kernel, pthread), process synchronisation (mutex, semaphore, monitors, producer-consumer, readers-writers, dining philosophers), deadlocks (conditions, prevention, avoidance — Banker's algorithm, detection), memory management (paging, segmentation, virtual memory, page replacement — LRU, FIFO, Optimal, thrashing), and file systems (directory structure, allocation methods, disk scheduling — SCAN, C-SCAN, LOOK).
Explain process vs thread." "What is a deadlock and how do you prevent it?" "How does virtual memory work?" "Compare paging vs segmentation." "Explain the classic producer-consumer problem." "What exactly is thrashing?" — These 6 questions appear in 80%+ of OS interviews.
How data is stored, organized, queried, and protected — the foundation of every application. ER modeling (entities, relationships, cardinality, weak entities), relational model (keys — primary, candidate, foreign, super), normalization (1NF → 2NF → 3NF → BCNF with examples), SQL depth (joins — INNER, LEFT, RIGHT, FULL, CROSS, self-joins; subqueries; aggregation — GROUP BY, HAVING; window functions — RANK, ROW_NUMBER, LEAD/LAG), transactions (ACID properties), concurrency control (locks, two-phase locking, timestamps, MVCC), indexing (B+ trees, hash indexing, clustered vs non-clustered, when to index vs not), and query optimization (EXPLAIN plans, index selection).
Explain normalisation with examples." "What are ACID properties?" "Difference between clustered and non-clustered index." "Write a query to find the 2nd highest salary." "What is a deadlock in DBMS?" "How does MVCC work?" — DBMS is the MOST tested CS fundamental across all companies.
How data travels from your browser to a server and back — the network knowledge every engineer needs. OSI model and TCP/IP stack (which layer does what), physical and data link layers (MAC addressing, ARP, switching, VLANs), network layer (IP addressing, subnetting and CIDR, routing — distance vector vs link state, IPv4 vs IPv6, NAT), transport layer (TCP — 3-way handshake, flow control, congestion control, reliable delivery; UDP — when to use which), application layer (DNS resolution, HTTP/HTTPS, REST, WebSockets, SMTP, FTP), and network security (TLS/SSL handshake, firewalls, VPN, common attacks — SYN flood, MITM, DNS spoofing)
Explain normalisation with examples." "What are ACID properties?" "Difference between clustered and non-clustered index." "Write a query to find the 2nd highest salary." "What is a deadlock in DBMS?" "How does MVCC work?" — DBMS is the MOST tested CS fundamental across all companies.
The language of databases — from basic queries to advanced analytics and procedural programming. DDL (CREATE, ALTER, DROP), DML (INSERT, UPDATE, DELETE), SELECT mastery (WHERE, ORDER BY, GROUP BY, HAVING, DISTINCT), joins (all types), subqueries (WHERE IN, EXISTS, correlated), set operations (UNION, INTERSECT, EXCEPT), aggregate and scalar functions, window functions (RANK, DENSE_RANK, ROW_NUMBER, NTILE, LEAD/LAG, running totals), CTEs and recursive queries, views and materialized views, PL/SQL (procedures, functions, cursors, triggers, exception handling, packages), and performance (EXPLAIN ANALYZE, index usage, query rewriting).
Write a query to find the Nth highest salary." "Difference between WHERE and HAVING." "Explain window functions with an example." "Write a query to find duplicate records." "What is a CTE and when would you use one?" — SQL is tested in EVERY technical interview, from service companies to FAANG.
The operating system that runs 96% of the world's servers — the command-line skills every developer and DevOps engineer needs. File system navigation (ls, cd, pwd, find, locate), file management (cp, mv, rm, mkdir, chmod, chown), permissions model (rwx, octal notation, setuid/setgid, umask), text processing (grep, sed, awk, cut, sort, uniq — the Swiss army knives of data manipulation), process management (ps, top, htop, kill, nohup, cron, systemctl), Bash scripting (variables, loops, conditionals, functions, command substitution, exit codes), piping and redirection (|, >, >>, 2>&1, tee), networking commands (ping, traceroute, netstat/ss, curl, wget, ssh, scp), user administration, and package management (apt, yum).
"How do Linux file permissions work?" "Find all files containing 'error' in /var/log." "Write a bash script to monitor disk usage and alert if >80%." "What is the difference between hard and soft links?" "How do you schedule a recurring task?" — Linux is tested at every DevOps, cloud, and backend role
Every question below has appeared in real placement interviews in the last 2 years. Each maps to a specific module. Students who can answer these confidently clear the technical interview round.
Tests DNS resolution → TCP handshake → TLS negotiation → HTTP request → server processing → response rendering. One question that covers 5 CN topics. The student who can explain this end-to-end demonstrates deep networking understanding
Process: independent, own memory space, expensive context switch. Thread: shared memory, lightweight, faster context switch. Multi-threading: concurrency within a process. Tests OS fundamentals — the question that separates "I memorised the definition" from "I understand the trade-offs."
Multiple solutions: correlated/nested subquery (SELECT MAX WHERE salary < MAX), DENSE_RANK window function, and dialect-specific LIMIT/OFFSET. The interviewer tests SQL fluency AND whether you know multiple approaches. The window function solution signals advanced SQL knowledge.
1NF (atomic values) → 2NF (no partial dependency) → 3NF (no transitive dependency) → BCNF (every determinant is a candidate key). The student who can explain WITH EXAMPLES ("a student-course table where...") demonstrates understanding, not memorisation.
find /var/log -name "*.log" -mtime -1. Tests practical Linux command knowledge. Follow-up: "Now grep for 'ERROR' in those files" → find ... -exec grep -l "ERROR" {} \;. Practical Linux skills are tested through scenarios, not definitions.
Atomicity (all or nothing), Consistency (valid state → valid state), Isolation (concurrent txns don't interfere), Durability (committed = permanent). Follow-up: "How does your database ensure Isolation?" → MVCC, locking. The answer depth reveals whether a student understands databases or just memorised acronyms.
TCS, Infosys, Wipro, Cognizant, Accenture, Deloitte, Amazon, Flipkart — EVERY technical interview includes OS, DBMS, and CN questions. Students who skip fundamentals for "trendy" topics lose offers in the technical round. CS fundamentals are not optional — they're the price of admission.
Interviewers don't accept textbook definitions. "Explain virtual memory" followed by "Why does thrashing happen?" and "How would you detect it?" — three levels of depth. This module teaches understanding through examples and scenarios, not rote definitions. Students who understand WHY answer follow-up questions confidently.
Product company system design questions (design a URL shortener, design a chat app) REQUIRE: database indexing (DBMS), TCP vs UDP (CN), caching and concurrency (OS), and server management (Linux). Students who skipped fundamentals can't answer system design — the interview round that determines senior-level packages.
Cloud computing = networking + Linux + OS. DevOps = Linux + networking + scripting. Backend development = databases + OS concepts + networking. Every specialised role builds ON CS fundamentals, not instead of them. A cloud engineer who can't explain TCP or DNS is a cloud engineer who can't debug production issues.
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