Best place to start

A clean first path for learners who want strong placement-oriented theory revision without drowning in too many sources.

Neso Academy
One of the best first stops if you want OS and CN explained clearly in an exam-friendly and placement-friendly style.
Operating Systems
A strong reading-based entry point when you want topic pages for common OS interview areas in one place.
Computer Network Tutorial
A practical place to begin CN revision once you need layered topic pages and common interview-friendly explanations.

Operating Systems

The OS resources that matter most for placements, interviews, and strong conceptual revision.

Operating Systems: Three Easy Pieces
One of the strongest OS resources anywhere once you want concepts like virtualization, concurrency, and persistence explained properly.
Operating Systems
Very useful for topic-by-topic OS revision when processes, threads, scheduling, deadlocks, and memory management need fast refreshers.
Neso Academy
A strong fit if you understand OS better from spoken walkthroughs than from textbook-style reading alone.
Operating System Interview Questions
Good for quick OS interview revision once you already know the basics and want clean Q-and-A style practice.

Computer Networks

The CN resources most likely to help with interview questions, viva rounds, and practical understanding.

Computer Network Tutorial
Useful for quick revision of OSI, TCP/IP, switching, routing, DNS, HTTP, and common network interview topics.
Beej's Guide to Network Programming
Excellent once you want networking to feel more practical through sockets and real communication flow, not only theory.
Gate Smashers
Helpful for placement-style CN explanation when you want a more direct theory-first teaching style.
Networking Interview Questions
A solid quick-revision list once you want the common CN interview questions grouped in one cleaner place.

OOP revision

Resources that make OOP interview concepts feel practical instead of memorized definitions.

OOPs Concepts in Java
A useful interview-oriented OOP refresher for encapsulation, inheritance, abstraction, polymorphism, and class design examples.
Java OOP (Object-Oriented Programming)
Good if you want a simpler OOP refresher with cleaner examples before revising tougher interview questions.
OOPs Interview Questions
Very useful when you want the common OOP interview questions asked in placements and first-job interviews.
Refactoring.Guru Design Patterns
Helpful after the basics when interview prep starts touching OOP design choices, patterns, and cleaner object modeling.

Channels

A small set of high-signal channels worth following for OS, CN, and OOP revision.

Neso Academy
Still one of the best all-round channels here for OS and CN theory revision with placement relevance.
Gate Smashers
Useful for DBMS-adjacent and core-CS theory revision when you want more direct and exam-style explanations.
Jenny's Lectures CS IT
A friendly option if you prefer slower pacing and more hand-holding for core CS revision.
Abdul Bari
Strong when you want clear conceptual explanations that help interview topics stick more deeply.
freeCodeCamp computer science videos
Useful for longer deep-dive CS videos and complete course-style refreshers in one place.

Websites

High-signal reading resources for topic-by-topic core CS interview revision.

Operating Systems
Best for quick OS topic refreshers when you need one searchable place for common placement questions.
Computer Network Tutorial
Useful for rapid CN revision across models, protocols, routing, error control, and networking terms.
Operating Systems: Three Easy Pieces
The strongest reading source here once you want OS concepts to feel intuitive rather than memorized.
Beej's Guide to Network Programming
A great bridge between CN theory and actual systems/networking intuition through simple practical examples.
Computer Science roadmap
Helpful when you want the big picture of where OS, networking, DBMS, and theory fit together in interview prep.

Revision notes / quick refreshers

Shorter revision-friendly resources for last-minute prep before interviews, assessments, and viva rounds.

Last Minute Notes - Operating Systems
A strong final-pass OS resource when time is short and you want the common topics condensed fast.
Last Minute Notes - Computer Network
Helpful for quick CN revision when protocols, layers, devices, and common terms start blurring together.
OOPs Interview Questions
A handy short OOP refresher once the big pillars and common interview comparisons need one fast pass.
Computer Science roadmap
Useful when you want to sanity-check what to revise next instead of guessing between subjects.

Books

A short core-CS book list that stays useful from revision through deeper understanding.

Operating Systems: Three Easy Pieces
Still the best free OS book here if you want real conceptual depth without poor textbook readability.
Operating System Concepts
A dependable college-style OS textbook when you want stronger formal grounding for interviews and exams.
Computer Networking: A Top-Down Approach
One of the strongest CN books for building intuition about protocols and layered communication.
Head First Object-Oriented Analysis and Design
Useful after OOP basics when you want object-oriented thinking to feel more practical and design-oriented.

Interview prep / revision resources

Resources that help with OS, CN, and OOP interview rounds without becoming a bloated dump of questions.

Operating Systems Interview Questions
Strong for campus and fresher prep when you want the most common OS interview questions grouped together.
Computer Network Interview Questions
Useful for quick CN revision before interviews when common protocol and networking questions need a refresher.
OOPs Interview Questions
A clean OOP interview list when inheritance, abstraction, interface vs abstract class, and polymorphism comparisons matter.
DBMS Interview Questions
Useful companion revision because many placement theory rounds ask DBMS alongside OS and CN, not separately.

Courses

Longer structured paths worth using when you want more guided revision than isolated notes can give.

Operating Systems: Three Easy Pieces
The strongest structured OS path here if you are ready to move beyond surface-level interview facts.
Intro to Database Systems
A deeper systems-style course worth knowing about once your core-CS revision starts leaning more serious than placements-only prep.
Neso Academy
Great if you want a channel-based study path you can actually follow subject by subject over time.
Gate Smashers
Useful when you want a more direct placement-style revision path across multiple core CS subjects.

Guide

Core CS interview prep

All the major OS, CN, and OOP revision resources a student usually needs in one place.

Best place to start

Start with one clear teaching channel, one reading source, and one interview question bank. Revise OS, CN, and OOP together instead of trying to master one subject fully before touching the others. Focus first on the recurring interview topics: processes, threads, deadlocks, paging, scheduling, TCP/IP basics, OSI, HTTP, DNS, OOP pillars, abstraction, inheritance, polymorphism, and common advantages or tradeoffs.

Who this is for

Students, freshers, and placement prep learners revising Operating Systems, Computer Networks, and OOP for interviews, technical rounds, and viva-style prep.

Best place to start

A clean first path for learners who want strong placement-oriented theory revision without drowning in too many sources.

3 resources

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Neso Academy

YouTubeFreeIndiaOS+1

One of the best first stops if you want OS and CN explained clearly in an exam-friendly and placement-friendly style.

Link

Operating Systems

GeeksforGeeks

WebsiteFreeOSPlacements+1

A strong reading-based entry point when you want topic pages for common OS interview areas in one place.

Link

Computer Network Tutorial

GeeksforGeeks

WebsiteFreeCNPlacements+1

A practical place to begin CN revision once you need layered topic pages and common interview-friendly explanations.

Link