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PREPARATION GUIDE

How To Prepare
Computer Science

Complete preparation strategy for all 10 subjects of Test II — Data Structures, OS, Algorithms, Networks, DBMS, COA, Digital Electronics, TOC, Discrete Math & Compilers.

70 Questions in Test II
105 Minutes
210 Marks (+3/-1/0)

Preparation Strategy

70 questions across 10 subjects — ~7 questions each. Breadth over depth is the key.

Critical Rule: BITS HD CS covers MORE topics than GATE CS 2026. Microprocessors (8085/8086), Network Security, Object-Oriented Data Models, and NP-Completeness are in BITS but NOT in GATE. Don’t skip these extras.
01

Phase 1: High PYQ Subjects

Data Structures, Operating Systems, COA

48 BITS PYQs combined. AVL trees, page replacement, CPU scheduling, pipelining, cache memory. These 3 subjects alone are 21 questions.

02

Phase 2: Theory & Memory-Heavy

Computer Networks, DBMS, Discrete Math

44 BITS PYQs. Subnetting, normalization, propositional logic. Lots of formulas — maintain a formula sheet.

03

Phase 3: Problem-Solving Subjects

Algorithms, TOC, Digital Electronics

32 BITS PYQs. Time complexity, DFA/NFA, undecidability, K-maps, MUX. Practice problems daily.

04

Phase 4: Revision & PYQs

Compiler Construction + Full Revision

Solve ALL BITS HD PYQs (128 questions) and relevant GATE PYQs (3000+). Focus on weak areas.

Time Management: 105 minutes for 70 questions = 1.5 min/question. CS questions are concept-based, not lengthy calculations. Spend 45-60 seconds per question. If stuck beyond 90 seconds, skip and return.

01 Foundational Subjects

42 BITS PYQs | Highest Impact

1. Data Structures Must Know — ~7 Qs, 17 BITS PYQs, GATE V2: 236 Qs

Most frequently asked subject in BITS HD! Focus on AVL trees, hashing, tree traversals, and stack/queue operations.

ADTs Algorithm Analysis Sorting Searching Linear Structures Hash Tables Search Trees Height Balancing Trees Graphs Partially Ordered Data
Key Topics & PYQ Patterns
AVL Trees
Min internal nodes for height h: N(h)=N(h-1)+N(h-2)+1. Balance factor ≤ 1. Rotations: LL, RR, LR, RL.
BITS PYQ: AVL rotation type identification and node count by height.
Hashing
Load factor = n/m. BITS PYQ: h=k%9 with linear chaining. Max linked list length? 4
Collision resolution: separate chaining, linear/quadratic probing, double hashing.
Tree Traversals
Inorder+Preorder OR Inorder+Postorder unique tree. BST Inorder = sorted.
BITS PYQ: Given two traversals, find the unique tree.
Stack/Queue
Circular queue overflow: (rear+1)%size==front. Stack reverses data stream.
BITS PYQ: Queue state after a sequence of enqueue/dequeue operations.
2. Operating Systems Must Know — ~7 Qs, 16 BITS PYQs, GATE V2: 335 Qs

Second most asked! Page replacement, CPU scheduling, deadlock, and process synchronization are the high-frequency topics.

Processes Threads Scheduling Concurrency Mutual Exclusion Deadlock Paging Segmentation Virtual Memory Page Replacement Thrashing File Systems I/O
Key Topics & PYQ Patterns
Page Replacement
FIFO: replace oldest. LRU: replace least recently used. Trace page faults step by step.
BITS PYQ: Given a reference string, count FIFO vs LRU page faults.
CPU Scheduling
Waiting Time = Turnaround - Burst. SJF non-preemptive, SRTF preemptive SJF.
BITS PYQ: FCFS, SJF, and RR scheduling — calculate waiting time.
Deadlock
4 conditions: Mutual Exclusion, Hold & Wait, No Preemption, Circular Wait. Break ANY one to prevent.
BITS PYQ: Banker’s algorithm — find safe sequence.
Process Sync
With interleaving: max = sum of increments, min = -(sum of decrements).
BITS PYQ: Two threads incrementing/decrementing a shared variable, find final range.
3. Computer Organization & Architecture Must Know — ~7 Qs, 15 BITS PYQs, GATE V2: 238 Qs

Pipelining and cache memory are the most tested topics. Master tag bit calculations and speedup formulas.

RISC & CISC Computer Arithmetic Control Unit Cache Memory Main Memory I/O RAID Pipelining Instruction-Level Parallelism Buses
Key Topics & PYQ Patterns
Pipelining
Ideal CPI = 1. Speedup = k (ideal). Hazards: structural, data, control.
BITS PYQ: Speedup with stalls due to data hazards.
Cache
Tag = Total addr bits - Index bits - Offset bits. BITS PYQ: 4-way set assoc, find tag bits.
Direct mapped, set associative, fully associative — know all three.
Address Space
256 TB = 248 bytes 48 bits. N bytes needs log2(N) bits.
BITS PYQ: Given memory size in TB, find address bus width.
2's Complement
n-bit range: -2(n-1) to 2(n-1)-1. Overflow when sign changes unexpectedly.
BITS PYQ: Overflow detection in signed addition.

02 Networking & Data

26 BITS PYQs

4. Computer Networks Must Know — ~7 Qs, 14 BITS PYQs, GATE V2: 215 Qs

Subnetting, TCP/UDP, and HTTP are the core. BITS also tests WiFi, Network Security, and Multicast Routing — topics NOT in GATE CS 2026.

LAN/MAN/WAN IEEE 802 Ethernet WiFi 802.11 IPv4 IPv6 Subnetting RIP OSPF BGP TCP UDP HTTP DNS DHCP SMTP Cryptography Firewalls IDS
Key Topics & PYQ Patterns
Subnetting
Subnet ID = IP AND mask. Broadcast = subnet ID OR (~mask). CIDR /24 = 24 network bits.
BITS PYQ: Given IP and subnet mask, find subnet ID and broadcast.
TCP/UDP
HTTP:80, HTTPS:443, FTP:21, SSH:22, DNS:53, SMTP:25. UDP max: 65535 bytes.
BITS PYQ: Well-known port numbers and protocol identification.
HTTP 1.0 vs 1.1
HTTP 1.1 = persistent (single TCP reused). 1.0 = non-persistent (new per object).
BITS PYQ: Object download time comparison for persistent vs non-persistent.
Sliding Window
Go-Back-N: W ≤ 2n - 1. Selective Repeat: W ≤ 2(n-1).
BITS PYQ: Given sequence number bits, find max window size.
5. Database Systems Must Know — ~7 Qs, 12 BITS PYQs, GATE V2: 284 Qs

Normalization is the most tested topic. Also focus on SQL joins, ER modeling, and transaction management (2PL).

ER Model Relational Model O-O Model Object-Relational Relational Algebra SQL Normalization FDs BCNF 4NF Indexing Query Optimization Transactions 2PL Crash Recovery
Key Topics & PYQ Patterns
Normalization
BCNF: every determinant is candidate key. BCNF guarantees ZERO redundancy.
BITS PYQ: Find highest normal form given FDs and candidate keys.
SQL Joins
Valid: INNER, LEFT, RIGHT, FULL OUTER, CROSS. PRODUCT and UNION are NOT join types.
BITS PYQ: Identify valid SQL join type from options.
Transactions
Strict 2PL: holds locks until commit. Wait-Die: older waits, younger dies.
BITS PYQ: Deadlock detection in wait-for graph.
Schema Levels
3 levels: External (user view), Logical/Conceptual, Internal/Physical (storage).
BITS PYQ: Data independence types — logical vs physical.

03 Algorithms & Theory

18 BITS PYQs

6. Discrete Mathematics Must Know — ~7 Qs, 18 BITS PYQs, GATE V1: 381 Qs

Highest BITS PYQ count! Combinatorics, functions/relations, and propositional logic. All topics overlap with GATE — no extra study needed.

Counting Recurrence Relations Sets Functions Relations Propositional Logic Predicate Logic Strings Languages
Key Topics & PYQ Patterns
Combinatorics
nCr, nPr, circular: (n-1)!. BITS PYQ: 8-bit strings with 5 ones? = C(8,5)=56
Pigeonhole, stars and bars, inclusion-exclusion.
Functions
1-1 functions from {A,B,C} to {1,2,3}? = 3! = 6. Total relations A×B: 2(|A|×|B|)
BITS PYQ: Count injective, surjective, bijective functions.
Logic
Truth tables, tautology, contradiction. Graphs: sum of degrees = 2|E|, odd-degree vertices always even.
BITS PYQ: Is a formula a tautology? Evaluate propositional logic.
7. Design & Analysis of Algorithms Must Know — ~7 Qs, 10 BITS PYQs, GATE V2: 334 Qs

BITS syllabus has EXTRA topics not in GATE 2026: Randomization, NP-Completeness, Backtracking, Branch-and-Bound, Approximation Algorithms. Don’t skip these!

Divide & Conquer Greedy Dynamic Programming Randomization Complexity Analysis Master Theorem Lower Bounds NP-Completeness NP-Hardness Reductions Backtracking Branch-and-Bound Approximation
Key Topics & PYQ Patterns
Master Theorem
T(n)=aT(n/b)+f(n). BITS PYQ: T(n)=2T(n1/2)+log n
Case 1: f(n) = O(nlogba - e). Case 2: f(n) = Θ(nlogba logkn). Case 3: f(n) = Ω(nlogba + e).
Sorting
Stable: Merge, Insertion, Bubble. Unstable: Quick, Heap, Selection.
BITS PYQ: Which sorting is stable? Lower bound of comparison sort: O(n log n).
Graph Algorithms
DFS/BFS: O(V+E) with adj list. BITS PYQ: DFS on complete graph using adj list? = O(V2)
Dijkstra, Bellman-Ford, Floyd-Warshall, Kruskal, Prim.
NP-Completeness
TSP paths: (n-1)!/2. Recursive uses MORE space than iterative.
BITS PYQ: NP-Completeness reductions — SAT, 3-COLORING, CLIQUE.
8. Theory of Computation Must Know — ~7 Qs, 8 BITS PYQs, GATE V2: 286 Qs

DFA/NFA, CFG closure properties, and undecidability are the key areas. Rice’s Theorem is heavily tested.

Regular Languages Regular Expressions DFA NFA CFG CFL PDA Pumping Lemma Turing Machines Universal TM Recursive Languages RE Languages Decidability
Key Topics & PYQ Patterns
DFA/NFA
Minimal DFA for a*b* has 2 states. NFA→DFA can have up to 2n states.
BITS PYQ: Count states in minimal DFA for a given language.
CFL Closure
CFL closed under: union, concatenation, Kleene star, reverse. NOT closed under: intersection, complement.
BITS PYQ: Is CFL closed under intersection? No!
Undecidability
For TM: Is L(M) empty/finite/regular/CFL? ALL undecidable. For DFA/CFG: emptiness IS decidable.
BITS PYQ: Rice’s Theorem — non-trivial semantic properties of TM are undecidable.
Pumping Lemma
anbn = CFL (not regular). anbncn = not CFL.
BITS PYQ: Use pumping lemma to prove a language is not regular.

04 Hardware & Systems

18 BITS PYQs

9. Digital Electronics & Microprocessors Must Know — ~7 Qs, 14 BITS PYQs, GATE V2: 303 Qs

BITS tests 8085/8086 microprocessors — NOT in GATE CS 2026. Also focus on K-maps, MUX, and flip-flops.

Adders MUX DeMUX Encoders Decoders Counters Registers PLDs Logic Families K-Maps 8085 8086 Memory Interfacing 8253 8255 8259 8251
Key Topics & PYQ Patterns
K-Maps
Group 1s for SOP, group 0s for POS. Simplify boolean expressions.
BITS PYQ: Given minterms, simplify using K-map.
MUX
2n inputs, n select lines, 1 output. Can implement any boolean function.
BITS PYQ: Given select lines and data, find output.
Flip-Flop vs Latch
KEY: Latch = level-triggered. Flip-Flop = edge-triggered (changes ONLY on clock edge).
BITS PYQ: Race-around condition in JK flip-flop if T > pulse width.
8085/8086
HLT: stop until interrupt. HOLD: DMA bus request. 8259 cascaded needs ICW1, ICW2, ICW3.
BITS PYQ: 8085 addressing modes, 8086 segmentation.
10. Compiler Construction Important — ~7 Qs, 4 BITS PYQs, GATE V2: 234 Qs

Lowest PYQ count but still 7 questions on the exam! Focus on compiler phases, CFG/parsing basics, and semantic analysis.

Lexical Analysis Parsing Top-Down Bottom-Up Abstract Syntax Tree Symbol Tables Semantic Analysis Type Checking Syntax Directed Translation Intermediate Code Code Generation Register Allocation
Key Topics & PYQ Patterns
Phases
Lexical→Syntax→Semantic→Intermediate Code→Optimization→Code Gen. Every CHARACTER seen in: Lexical Analysis.
BITS PYQ: Which phase handles character-level scanning?
Grammar
CFG = syntax. Attribute Grammar = semantics AND syntax. Type checker = semantic phase.
BITS PYQ: Attribute grammars and inherited vs synthesized attributes.
Parsing
LL = top-down, LR = bottom-up (more powerful). FIRST/FOLLOW sets.
BITS PYQ: Compute FIRST and FOLLOW sets for a given grammar.

Final Tips for Computer Science

70 questions in 105 minutes — every subject matters equally.

Scoring Strategy:
• Data Structures, OS, COA = 21 questions, highest PYQ frequency. Master these 3 first.
• Don’t skip “extra” topics — Microprocessors, Network Security, NP-Completeness appear in BITS but NOT in GATE.
• Maintain a formula sheet: cache tag bits, page replacement traces, subnetting, normalization rules.
• Time: 1.5 min/question. Concept-based, not calculation-heavy. If stuck >90 sec, skip.
• Solve ALL 128 BITS HD PYQs — many questions repeat in spirit.

Recommended Books & Resources

These textbooks + GATE PYQs cover everything. No need for paid courses.

Free Practice Sources
• GateOverflow PYQs ↗ — All CS PYQs with solutions
• GATE PYQs (Volume 2) ↗ — ~3000+ CS Questions PDF
• BITS HD PYQ Analysis ↗ — 128 CS Questions mapped to topics
+3
Correct Answer
-1
Wrong Answer
Unattempted