CS Fundamentals Resource :Lets Code

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1	CS FUNDAMENTALS RESOURCE KIT
2	Operating Systems \| DBMS \| Computer Networks \| OOP \| Let's Code
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4	Follow me on X for more Tech Resources - Avinash Singh
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6	WHAT THIS IS
7		The four subjects every technical interview in India tests: Operating Systems, DBMS, Computer Networks and OOP. More candidates are rejected here than in the coding round, because most people learned these for exams rather than for interviews and cannot explain them out loud.
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9	HOW TO USE IT
10		1. Open 'Roadmap' first. It sequences all four subjects across 52 weeks with a practice target for each.
11		2. 'Most Asked' is the highest-value sheet. 61 questions with what a good answer actually covers, ranked by how often they appear.
12		3. 'Key Comparisons' is the second. 42 A-versus-B questions, because most CS core questions are comparisons in disguise.
13		4. Use 'Skills Matrix' as your subject-by-subject checklist. Filter by Category to study one subject at a time.
14		5. 'Where It Is Asked' tells you which companies weight which subjects. A TCS interview and a Google interview test completely different things.
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16	THE HONEST ADVICE
17		A definition scores half marks. An example scores full marks. For every concept, prepare a one-line example from code you have actually written.
18		Explain in 60 seconds, then stop. Most candidates know the answer and lose marks by rambling past it.
19		Written rounds are mostly numericals. Scheduling, page replacement, subnetting, normalisation and CRC. Drill these against a timer.
20		This knowledge fades faster than DSA. Revise one subject weekly in rotation, permanently, or you will lose it in a month.
21		Service companies weight CS core more heavily than product companies do. If TCS, Infosys or Accenture are your target, this vault matters more to you than the DSA one.
22		Say 'I do not know' cleanly when you do not. Bluffing on OS internals is transparent and costs more than the missing answer.
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24	BUILT BY
25		Avinash Singh, founder of Let's Code (lets-code.co.in): free AI career tools, 1000+ resources and a community of 100k+ engineers.
26		Follow on X for updates and new resource drops: https://x.com/AvinashSingh_20
27		See the Lets Code Resources sheet for PYQs, interview experiences and the full free toolkit.
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29	LEVEL KEY
30		Foundation = guaranteed to be asked. Core = expected in most technical rounds. Advanced = depth that differentiates you.
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32	CONTENTS
33	#	Sheet	What is in it	Entries
34	1	Skills Matrix	Every topic across all four subjects, and how each is tested	116
35	2	Roadmap	52-week plan covering all four subjects, with practice targets	14
36	3	Most Asked	61 questions ranked by frequency, with what a good answer covers	61
37	4	Key Comparisons	42 A-versus-B questions, the format most CS core questions take	42
38	5	Free Courses	Free courses, textbooks and university material by subject	48
39	6	YouTube	Direct playlists by subject, in English and Hinglish	26
40	7	GitHub Resources	Curricula, question banks and placement preparation repos	30
41	8	Books & Docs	The standard textbooks plus the free alternatives worth using	32
42	9	Practice & Labs	Numerical practice, SQL, subnetting, simulators and mocks	29
43	10	Communities	Communities, creators, institutions and newsletters	35
44	11	Where It Is Asked	Which companies weight which subjects, and in what format	58
45	12	Lets Code Resources	Free AI tools, PYQs and community from Lets Code	34
46			TOTAL RESOURCES	525
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48	Links compiled July 2026. Every YouTube URL is a direct playlist or video sourced from EbookFoundation/free-programming-books and curated university indexes, not reconstructed from memory, and there are no channel-only links. The YouTube sheet has a Language column: 21 rows are English and 5 are Hinglish. Gate Smashers, Knowledge Gate and Bitten Tech teach in Hinglish and are included because they are the most used CS core resources in India; filter the column if you want English only. Company weightings are drawn from publicly reported interview experiences and vary by role, year and interviewer.
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