DEEP ANALYSIS
BITS HD 2026
Important Topics Guide
Everything you need to study - based on 3000+ GATE questions, 180+ BITS PYQs, and the official syllabus. No confusion, just clarity.
Exam: 25 & 26 May 2026
Understand the Exam First
Before studying, be crystal clear about what you're preparing for.
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Read Carefully: The BITS HD exam has separate papers. Which papers YOU write depends on your program choice. Don't prepare for the wrong test!
Compulsory for ALL
Test I
Part A: Core Mathematics (15 Qs)
Part B: English + Logical Reasoning (15 Qs)
Written by: Everyone applying to ANY HD program
For M.E. Computer Science
Test II (CS)
10 CS subjects, ~7 questions each:
DSA, Algorithms, OS, Networks, DBMS, TOC, COA, Digital Electronics, Discrete Math, Compilers
Written by: M.E. CS applicants only. GATE CS score also accepted (50% seats each route).
For M.E. Software Systems
SS Special Test
C Programming (~15-20 Qs), OOP & Software Engineering (~10-12 Qs), Database (~8 Qs), Core Systems (~10 Qs)
Written by: M.E. Software Systems applicants ONLY. GATE score NOT accepted for SS.
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Key Facts:
• MCQ with 4 options, only 1 correct. Cannot select multiple.
• All questions in English only.
• Online Computer-Based Test (CBT).
• M.E. Software Systems: ONLY through BITS HD Test (no GATE shortcut).
• M.E. CS: 50% seats via GATE, 50% via BITS HD Test.
01 Test I — Core Mathematics
15 Questions • Part of 45-min paper • Compulsory for everyone • Engineering math level
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From BITS PYQs Analysis: Complex Variables and Probability appear EVERY year without exception. These alone can give you 4-6 questions out of 15. Linear Algebra is the third most frequent. Prepare these three first.
Probability & Statistics
Must Do - Every Year
GATE: 107 Questions
BITS PYQs: 8+ Direct Questions
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Poisson DistributionMust Know
Formula: P(X=k) = (e^(-λ) · λ^k) / k! — Know how to find λ from conditions like P(X=1)=P(X=2)
BITS PYQ: "In a Poisson distribution, if P(x=1) = P(x=2), find P(x=4)." → Solve: λ=2, then P(x=4) = (e^-2 * 16)/24 = (2/3)e^2
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Bayes' Theorem & Total ProbabilityMust Know
P(A|B) = P(B|A)·P(A) / P(B). Total Probability: P(B) = Σ P(B|Ai)·P(Ai)
BITS PYQ: "Election probabilities A=1/3, B=2/9, C=4/9. Ladies admitted: 0.2, 0.3, 0.5 if A/B/C win. Find P(woman admitted)." → Use total probability theorem
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Expected Value E(X)Must Know
E(X) = Σ x·P(X=x) for discrete. E(X) = ∫ x·f(x)dx for continuous. Var = E(X²) - [E(X)]²
BITS PYQ: "3 white, 5 red balls. Pick 2. Rs.10/white, Rs.35/red. Find expected value." Also: "p(x)=kx² is PDF, find E(x)"
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Binomial DistributionImportant
P(X=k) = C(n,k) · p^k · (1-p)^(n-k). Mean = np, Variance = npq
BITS PYQ: "3 foods, 2 alike. Man picks odd one (p=1/3). In 5 trials, P(4+ correct)?" → P(4)+P(5) using binomial
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Set Operations on Events (P(A∪B), De Morgan's)Important
P(A∪B) = P(A)+P(B)-P(A∩B). Mutually exclusive: P(A∩B)=0. P(A'∩B') = 1-P(A∪B)
BITS PYQs: "Given P(A'), P(B'), P(A∪B), find P(A∩B)" + "P and Q mutually exclusive, find P(A'∩B')"
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Birthday ProblemGood to Know
P(3 specific people share exact same birthday) = (1/365)²
BITS PYQ: Direct MCQ with options 1/365, 1/(365)², 1/(365)³. Answer: 1/(365)²
Linear Algebra
Must Do - Every Year
GATE: 102 Questions
BITS PYQs: 5+ Questions
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Eigenvalues & EigenvectorsMust Know
Solve det(A - λI) = 0 for eigenvalues. Then (A-λI)x = 0 for eigenvectors. Properties: sum = trace, product = determinant.
GATE has 33 questions on this alone! BITS PYQ explicitly mentions "evaluating eigenvectors." Practice 3×3 matrices thoroughly.
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Rank of Matrix & Systems of EquationsMust Know
Row reduce to echelon form. Rank = non-zero rows. For Ax=b: if rank(A)=rank([A|b])=n → unique solution; <n → infinite; unequal ranks → no solution.
BITS PYQ: "Questions evaluating matrix rank and vector spaces in Linear Algebra." GATE has 17+22 questions on systems & matrices.
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DeterminantsImportant
Cofactor expansion along row/column. Properties: det(AB)=det(A)det(B), det(kA)=k^n·det(A), det(A^T)=det(A).
Needed for eigenvalue computation. Know shortcuts for 3×3 determinants (Sarrus' rule).
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Vector Spaces (Basis, Dimension)Good to Know
Basis = linearly independent spanning set. Dim = number of basis vectors. Rank-Nullity: dim(V) = rank(T) + nullity(T).
Explicitly in syllabus. BITS PYQ mentions "vector spaces." GATE has 6 questions on this.
Complex Variables
Must Do - BITS Favourite!
BITS PYQs: 6+ Questions - Asked EVERY session!
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Residue CalculationMust Know
Simple pole at z=a: Res = lim(z→a) [(z-a)·f(z)]. For essential singularity: use Laurent series and pick coefficient of 1/(z-a).
BITS PYQ: "Find residue of z·cos(1/z)" → Laurent expand cos(1/z) = 1 - 1/(2z²) + ..., multiply by z, find coeff of 1/z term.
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Roots of sin(z)=0, Complex EquationsMust Know
sin(z)=0 only when z=nπ (all real). cosh(z)+sinh(z)=e^z, so e^z=-i means z=i(-π/2+2nπ).
BITS PYQ: "Find roots of f(z)=sin(z)=0" Options: nπ, nπi, 2nπ, 2nπi. Answer: nπ. Also: "Solve cosh(z)+sinh(z)=-i"
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Evaluate i^i (Memorize This!)Important
i^i = e^(i·ln(i)) = e^(i·iπ/2) = e^(-π/2) ≈ 0.2079. This is a REAL number!
BITS PYQ: "Evaluate i^i" Answer provided: e^(-π/2). Just memorize this result - it's asked directly.
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Analytic Functions & Cauchy-RiemannGood to Know
f=u+iv is analytic if ∂u/∂x=∂v/∂y and ∂u/∂y=-∂v/∂x. Cauchy's integral formula: f(a) = (1/2πi)∮f(z)/(z-a)dz
In official syllabus. Know how to verify analyticity and apply Cauchy's theorem.
Calculus (Single & Multivariable)
High Priority
GATE: 63 Questions
BITS PYQs: 5+ Questions
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Maxima & MinimaMust Know
Find f'(x)=0, check f''(x). Also check endpoints and points where derivative doesn't exist (fractional exponents).
BITS PYQ: "Find maxima of f(z)=6z^(1/3)-12z^(4/3) in [-1,1]" → Derivative undefined at z=0, also check z=±1
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Series Convergence (p-series)Must Know
Σ(1/n^p): converges if p>1, diverges if p≤1. Also know ratio test: lim|a_{n+1}/a_n| < 1 converges.
BITS PYQ: "At what value of p does Σ(1/n^p) converge or diverge?" → Converges when p>1
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Polar Coordinates (Area & Arc Length)Important
Area = ½∫r²dθ. Arc length = ∫√(r²+(dr/dθ)²)dθ. Conics: r=ed/(1+ecosθ)
BITS PYQs: "Area inside unit circle but outside r=1-cosθ" + "Arc length" + "r=25/(1+cosθ), find eccentricity" (e=1, parabola)
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Green's/Stokes/MVTGood to Know
Green's: ∮(Pdx+Qdy) = &iint;(∂Q/∂x-∂P/∂y)dA. MVT: f(b)-f(a)=f'(c)(b-a) for some c in (a,b).
BITS PYQ: "Apply MVT and Green's theorem to find the required z value and span"
Differential Equations & Transforms
Medium - 1-2 Questions
BITS PYQs: 3 Questions
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Cauchy-Euler EquationImportant
Form: x²y'' + axy' + by = 0. Substitute y=x^m → m(m-1)+am+b=0. Solve quadratic for m.
BITS PYQ: "Solve a given Cauchy-Euler equation" → Direct substitution method
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Laplace TransformImportant
L{1}=1/s, L{t^n}=n!/s^(n+1), L{e^at}=1/(s-a), L{sin(at)}=a/(s²+a²). Inverse also needed.
BITS PYQ: "Find the Laplace transform" → Direct formula application
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Even/Odd Function IdentificationGood to Know
Even: f(-x)=f(x) [symmetric about y-axis]. Odd: f(-x)=-f(x) [origin symmetric]. u[n]-u[n-4] type signals.
BITS PYQ: "For what value is even part of f(n)=u[n]-(n-4) guaranteed to be zero? |n|<4"
02 Test I — English & Logical Reasoning
15 Questions • ~8 English + ~7 Reasoning • Easy marks if you practice • Don't ignore this!
English Language (~8 Questions)
High - Easy Marks
GATE V1: 376 Verbal Questions
BITS PYQs: 12 Questions
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Prepositions (Fixed Phrases)Must Know
"apply FOR a job", "died OF a disease", "depend ON", "consist OF", "agree WITH someone", "agree TO a proposal"
BITS PYQ: "What job will you apply ___ in the future?" Answer: FOR. Also: "died of/from some disease" → "died of"
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Sentence RearrangementMust Know
Find opening sentence (general/topic). Then arrange by logical flow: time order, cause-effect, general-to-specific.
BITS PYQ: "Rearrange 5 jumbled phrases to form a coherent sentence" → Practice 10-15 of these
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Reading ComprehensionMust Know
Answer ONLY from passage, not general knowledge. Look for main idea, tone, specific details. Eliminate wrong options.
BITS PYQs: "Draw logical conclusion from passage" + "Select sentence with similar meaning to given sentence"
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Vocabulary & Word MeaningsImportant
"Circumspect"=cautious. Learn 200 commonly tested GRE/GATE words. Focus on synonyms and contextual meanings.
BITS PYQ: "Identify correct meaning of 'circumspect'" + "Identify synonym from four options"
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Grammar (few vs a few, tenses)Important
"Few"=hardly any (negative). "A few"=some (positive). "Less"=uncountable. "Fewer"=countable.
BITS PYQ: "Grammatical difference between 'few' and 'a few'?" + "Are theories 'accepted' or 'refuted'?"
Logical Reasoning (~7 Questions)
High - Pattern Recognition
GATE V1: 139 Analytical + 49 Spatial Qs
BITS PYQs: 4+ Questions
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Number/Letter SeriesMust Know
Find pattern: constant difference, increasing difference, multiply, squares, cubes, alternating operations.
BITS PYQ: "Numerical patterns and series completion" → Practice identifying hidden patterns
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Figure/Pattern CompletionImportant
Quarter missing from pattern. Check: rotation (90°/180°), reflection, progression (shading increases), alternating elements.
In syllabus: "Pattern Perception - identify correct quarter from 4 alternatives"
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Analogy & Odd One OutImportant
Find relationship in given pair, apply same logic. For odd-one-out: 3 items share a property, 1 doesn't.
Explicitly in BITS syllabus. Common types: word analogy, number analogy, symbol analogy.
03 Test II — Computer Science (10 Subjects)
70 Questions • 105 Minutes • ~7 Qs per subject • 1.5 min/question • Easier than GATE, concept-focused
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Strategy: Questions are concept-based (not lengthy calculations). Know definitions, properties, and basic problem-solving for each topic. If you know GATE basics, you'll find these easier. Don't skip ANY subject - each has ~7 guaranteed questions.
Algorithms & Complexity
Critical - ~7 Questions
GATE V2: 334 Questions (Largest!)
BITS PYQs: 10 Questions
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Time Complexity & Master TheoremMust Know
Master theorem: T(n)=aT(n/b)+f(n). Compare f(n) with n^(log_b(a)). Also know: nested loops, log patterns.
BITS PYQ: "Find complexity of T(n)=2T(n^(1/2))+log n" + "For what n is f(n)=n²-n+550 faster than g(n)=59n+50?"
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Sorting (Selection, Properties, Best Fit)Must Know
Stable: Merge, Insertion, Bubble. Unstable: Quick, Heap, Selection. Best for small range: Counting/Bucket. Large range: Quick/Merge.
BITS PYQ: "Best sort for (i) 1-100 integers (ii) 0-1M integers?" + "What is a stable sorting algorithm?" + "Find median of 10 sorted elements" O(1)
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Graph Algorithms (DFS, BFS, Dijkstra, MST)Must Know
DFS/BFS: O(V+E) with adj list, O(V²) with adj matrix. Dijkstra: O((V+E)logV) with heap. Prim's/Kruskal's for MST.
BITS PYQ: "DFS on complete graph using adjacency list?" → O(V²) since E=V(V-1)/2
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Design Paradigms (Greedy, DP, D&C)Important
Greedy: Prim's, Kruskal's, Dijkstra, Huffman. DP: Floyd-Warshall, LCS, Matrix Chain, Knapsack. D&C: Merge Sort, Quick Sort, Binary Search.
GATE frequently asks "match algorithm to paradigm" questions. Know which technique each algorithm uses.
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TSP, NP-Completeness, Recursive vs IterativeGood to Know
TSP paths: (n-1)!/2. Recursive uses MORE space than iterative (stack frames). NP-hard means no known poly-time solution.
BITS PYQs: "Paths for TSP with 10 vertices?", "Which is FALSE? Recursive uses LESS space" (This is false!)
Data Structures
Critical - Most Asked in BITS!
GATE V2: 236 Questions
BITS PYQs: 17 Questions (Highest!)
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AVL Trees (Balance, Min Nodes, Insertions)Must Know
Balance factor |h(left)-h(right)| ≤ 1. Min nodes for height h: N(h)=N(h-1)+N(h-2)+1. Rotations: LL, RR, LR, RL.
BITS PYQs: "Max height difference?" → 1. "Min internal nodes for height 5?" "Which sequence needs NO rotation? 4 3 1 2 5"
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Tree Traversals & ReconstructionMust Know
Inorder+Preorder OR Inorder+Postorder → unique tree. BST Inorder = sorted. Preorder of BST is unique.
BITS PYQ: "Inorder=ABCDEFG, Postorder=ACBEGFD → Find Preorder" + "Which traversal gives sorted order?" → Inorder
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Hashing (Chaining, Probing)Must Know
Linear chaining: linked list per slot. Open addressing: probe sequence. Load factor = n/m. Good hash = uniform distribution.
BITS PYQ: "h=k%9 with linear chaining. Find max linked list length formed." Answer: 4
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Stack & Queue (Overflow Conditions)Must Know
Circular queue overflow: (rear+1)%size==front. Two stacks in array: top1+1==top2. Stack reverses data stream.
BITS PYQs: "Circular queue overflow?", "Two stacks - overflow condition?", "ADT to reverse stream?" → Stack
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Linked List & Array DifferencesImportant
Array: O(1) access, fixed size. Linked List: O(n) access, dynamic size, O(1) insertion at head.
BITS PYQ: "Search complexity in linked list?" → O(n). "Difference between Array and Linked List?"
Operating Systems
Critical - ~7 Questions
GATE V2: 335 Questions
BITS PYQs: 16 Questions
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Page Replacement (FIFO, LRU, Optimal)Must Know
Trace page faults step by step. FIFO: replace oldest. LRU: replace least recently used. Optimal: replace one used farthest in future.
BITS PYQ: "Find page faults using FIFO and LRU for a given string" → You MUST trace every step
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CPU Scheduling (SJF, RR, SRTF)Must Know
Waiting Time = Turnaround - Burst. Turnaround = Completion - Arrival. SJF is non-preemptive. SRTF is preemptive SJF.
BITS PYQs: "5 processes at t=0, find average waiting time (SJF)" + "Average turnaround time (Round Robin)"
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Deadlock (Conditions & Solutions)Must Know
4 necessary conditions (ALL must hold): Mutual Exclusion, Hold&Wait, No Preemption, Circular Wait. Break ANY one to prevent.
BITS PYQs: "Under which condition no deadlock?", "Wait-for graph used for?" → Detection. "Deadlock-free?" → Wait and Die
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Process Synchronization & ConcurrencyMust Know
Race conditions with shared variables. With interleaving: max = sum of all increments, min = -(sum of all decrements). Semaphores: wait() decrements, signal() increments.
BITS PYQ: "X=0, two loops (X++; X--) each run 10 times. Min & max of X?" → Min=-10, Max=20
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Process States & ThreadsImportant
INVALID transition: Blocked→Running (must go via Ready first!). Threads share address space. Thread = lightweight process.
BITS PYQs: "Which transition NOT valid?" → Blocked to Running. "True about threads?" → Lightweight process
Computer Networks
Critical - ~7 Questions
GATE V2: 215 Questions
BITS PYQs: 14 Questions
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Subnetting & IP AddressingMust Know
Subnet ID = IP AND mask. Broadcast = subnet ID OR (~mask). CIDR /24 means 24 network bits, 8 host bits.
BITS PYQ: "Given IP and CIDR mask, find subnet ID and broadcast address" → Practice 5-10 problems
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TCP/UDP & Port NumbersMust Know
HTTP:80, HTTPS:443, FTP:21, SSH:22, DNS:53, SMTP:25, SQL Server:1433. UDP max packet: 65535 bytes. Client uses ephemeral port (>1023).
BITS PYQs: "SQL server port?", "Max UDP packet size?" → 65535. "Client can't use port ___ for HTTP?" → 80 (server's port)
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HTTP 1.0 vs 1.1 (Persistent Connections)Must Know
HTTP 1.1 = persistent (single TCP connection reused). HTTP 1.0 = non-persistent (new connection per object).
BITS PYQ: "10 objects with HTTP 1.1 → how many TCP connections?" Answer: 1 (persistent connection)
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Sliding Window & Go-Back-NImportant
Efficiency = W·Tf/(Tf+2Tp). Window size for Go-Back-N: W ≤ 2^n - 1. For Selective Repeat: W ≤ 2^(n-1).
BITS PYQ: "Calculate Go-Back-N efficiency given bandwidth, RTT, frame length, window size"
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OSI Layers, ARP, ICMPGood to Know
Ethernet 802.3 = Layer 2 (Data Link). ARP: IP→MAC. ICMP goes inside IP packet, then inside frame.
BITS PYQs: "Ethernet 802.3 OSI layer?" → Data Link. "ARP maps?" → IP to MAC. "ICMP enclosed where?" → IP then frame
Database Systems
Critical - ~7 Questions
GATE V2: 284 Questions
BITS PYQs: 12 Questions
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Normalization (NFs, BCNF = No Redundancy)Must Know
1NF: atomic. 2NF: no partial dependency. 3NF: no transitive. BCNF: every determinant is candidate key. BCNF guarantees ZERO redundancy.
BITS PYQ: "Relation decomposed into BCNF - redundancy level?" → Zero/None
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SQL Joins & QueriesMust Know
Valid SQL joins: INNER, LEFT, RIGHT, FULL OUTER, CROSS. "PRODUCT" and "UNION" are NOT join types (they're set operations).
BITS PYQs: "Not a valid SQL join?" → Union/Product. "SELECT colors FROM R GROUP BY colors" → gives distinct colors
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ER Model & Schema LevelsMust Know
3 levels: External (highest, user view), Logical/Conceptual (middle), Internal/Physical (lowest). M:N relationship attributes go IN the relationship.
BITS PYQ: "Highest abstraction schema?" → External. "Hotel-Lodging M:N: where is 'Total rent'?" → In Lodging (relationship)
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Transactions (2PL, Strict 2PL, Wait-Die)Important
Strict 2PL: holds all locks until commit → prevents cascading rollbacks. Wait-Die: older waits, younger dies (restarts) → deadlock-free.
BITS PYQs: "No cascading rollbacks?" → Strict 2PL. "Deadlock-free?" → Wait and Die
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Keys & CheckpointsGood to Know
Super Key: closure = all attributes. Candidate Key: minimal super key. Checkpoints reduce REDO work (not undo).
BITS PYQs: "Attributes giving R itself?" → Super Key. "Checkpoints reduce?" → Redo work
Digital Electronics & Microprocessors
Critical - ~7 Questions
GATE V2: 303 Questions
BITS PYQs: 14 Questions
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K-Maps, SOP/POS, Minterms/MaxtermsMust Know
K-map: group 1s for SOP, group 0s for POS. Minterm m_i: binary representation where output=1. Maxterm M_i: where output=0.
BITS PYQ: "Which expression gives POS?", "Find minterm 15 and maxterm 12 for f(A,B,C,D)"
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MUX, Decoder, Combinational CircuitsMust Know
MUX: 2^n inputs, n select lines, 1 output. Can implement any boolean function. Decoder: n inputs, 2^n outputs (one-hot).
BITS PYQ: "Mystery device: multiple inputs, select lines, single output based on selection" → Multiplexer
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Flip-Flop vs LatchMust Know
KEY DIFFERENCE: Latch = level-triggered (transparent when enable=1). Flip-Flop = edge-triggered (changes ONLY on clock edge).
BITS PYQ: "Difference between latch and flip-flop?" → Level-triggered vs Edge-triggered
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Number Codes & Logic GatesImportant
Gray code: adjacent differ by 1 bit. Binary→Gray: MSB same, rest=XOR of adjacent. Three output states: High, Low, High-Impedance.
BITS PYQs: "Gray→Excess-3 conversion", "Reverse XOR I/O → which gate?", "Three output states?"
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8085/8086 BasicsGood to Know
HLT: stop until interrupt. HOLD: DMA bus request. LOCK: bus lock. 8259 cascaded: needs ICW1, ICW2, ICW3.
BITS PYQs: "8085 sleep mode instruction?" → HLT. "HOLD signal in 8086?", "8259 cascaded mode ICWs needed?"
Computer Organization & Architecture
Critical - ~7 Questions
GATE V2: 238 Questions
BITS PYQs: 15 Questions
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Pipelining (CPI, Speedup, Hazards)Must Know
Ideal CPI = 1 for k-stage pipeline. Speedup = k (ideal). Real speedup limited by hazards (structural, data, control).
BITS PYQs: "Ideal CPI of 5-stage RISC?" → 1. "Pipelining prefers low CPI + high clock rate." "Performance factors?"
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Cache Memory (Tag Bits Calculation)Must Know
Tag bits = Total address bits - Index bits - Offset bits. Index = log2(sets). Offset = log2(block size). Sets = cache_size/(block_size × associativity).
BITS PYQ: "4-way set associative, given memory size, block size, main memory → find tag bits"
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Address Space & BitsMust Know
256 TB = 2^48 bytes → needs 48 bits. General: N bytes addressable space needs log2(N) bits for addressing.
BITS PYQ: "256 TB virtual address space needs how many bits?" → 48. "Reduce bits by 2, double addressability → total space?"
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Von Neumann, Buses, Locality, RAIDImportant
Von Neumann: CPU+Memory+I/O+Bus (NOT network card). Control bus carries R/W signals. Code=temporal, Data=spatial locality. RAID: striping=performance, mirroring=reliability.
BITS PYQs: "Not von Neumann?" → Network card. "R/W signals?" → Control bus. "Locality in matrix mult?" → Code=temporal, Data=spatial
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2's Complement & OverflowGood to Know
n-bit range: -2^(n-1) to 2^(n-1)-1. Overflow: adding two positives gets negative, or two negatives gets positive.
BITS PYQ: "15-bit 2's complement largest range?" → -2^14 to 2^14 - 1
Theory of Computation
Critical - ~7 Questions
GATE V2: 286 Questions
BITS PYQs: 8 Questions
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DFA/NFA & Regular ExpressionsMust Know
Minimal DFA for a*b* has 2 states. NFA→DFA can have up to 2^n states. DFA→regex: state elimination.
BITS PYQs: "States in DFA for a*b*?" → 2. "NFA to DFA complexity?" → Exponential (up to 2^n states)
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CFG/CFL Closure PropertiesMust Know
CFL closed under: union, concatenation, Kleene star, reverse. NOT closed under: intersection, complement.
BITS PYQ: "Is CFG closed under union, complement?" → Closed under union, NOT under complement
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Undecidability (Rice's Theorem)Must Know
For TM: "Is L(M) empty/finite/regular/CFL?" ALL undecidable (Rice's theorem). For DFA/CFG: emptiness IS decidable.
BITS PYQ: "Let M be CFG. Which undecidable?" → L(M) is regular. (Emptiness of CFG IS decidable!)
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Pumping Lemma & Language ClassificationImportant
Used to prove NOT regular/CFL. a^n b^n = CFL (not regular). a^n b^n c^n = not CFL. a*b* = regular. ww^R = CFL.
BITS PYQs: "Pumping lemma theory question" + "Identify CFL vs Regular Languages"
Discrete Mathematics
Critical - ~7 Questions
GATE V1: 381 Questions Total
BITS PYQs: 18 Questions
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Combinatorics (P&C, Circular Permutation)Must Know
nCr, nPr, circular: (n-1)!, with constraints (sitting together: treat as block). Binary strings with k ones: C(n,k).
BITS PYQs: "Circular arrangement, 8 people, 2 together?" → 6!×2!. "8-bit strings with 5 ones?" → C(8,5)=56
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Functions & RelationsMust Know
1-1 functions from n to n: n!. Total relations A×B: 2^(|A|×|B|). Equivalence: reflexive+symmetric+transitive.
BITS PYQs: "1-1 functions from {A,B,C} to {1,2,3}?" → 3!=6. "Relations in A×B, |A|=|B|=2?" → 2^4=16
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Propositional Logic & Graph TheoryImportant
Truth tables, tautology, contradiction. Graphs: sum of degrees = 2|E|, odd-degree vertices always even count.
GATE has 77 Logic + 83 Graph Theory questions. Know basic properties and De Morgan's laws.
Compiler Construction
High - ~7 Questions
GATE V2: 234 Questions
BITS PYQs: 4 Questions
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Phases of CompilerMust Know
Lexical→Syntax→Semantic→Intermediate Code→Optimization→Code Gen. Every CHARACTER seen in: Lexical Analysis.
BITS PYQ: "Compiler encounters every character in which phase?" → Lexical Analysis
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Grammar & Semantics DescriptionMust Know
CFG = syntax. Attribute Grammar = semantics AND syntax. Type checker ensures type compatibility (semantic phase).
BITS PYQs: "Describes semantics/syntax of C?" → Attribute Grammar. "Type checker responsibility?" "Linker purpose?"
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Parsing & Code GenerationGood to Know
LL = top-down, LR = bottom-up (more powerful). FIRST/FOLLOW sets. Register allocation in code gen phase.
GATE has 20 LR + 27 Parsing questions. Know basic difference between LL and LR parsing.
04 Software Systems Special Test
50 Questions • 60 Minutes • 150 Marks • ONLY for M.E. SS • No GATE accepted • C Programming dominates!
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For SS Students: C Programming is ~30-40% of this paper! Pointers, macros, fork(), unions, storage classes - these are asked EVERY year. If you master C, you've already secured major marks. OOP/SE is conceptual (no coding, just theory).
C Programming (Structured + Advanced)
Critical - ~15-20 Questions!
GATE V2: 127 Questions
BITS PYQs: 10 Questions
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Pointers & Address ArithmeticMust Know
*p = value at address p. &x = address of x. Pointer arithmetic: p+1 moves by sizeof(*p) bytes. Array name = pointer to first element.
BITS PYQ: "Swap function with pointers - predict output." Key: passing by pointer allows modification of original values.
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Macros (#define) - Text Substitution!Must Know
Macros do LITERAL text replacement. No parentheses = bugs! #define f(A,B) A+B means f(2,3) becomes 2+3 (not (2+3)).
BITS PYQ: "#define f(A,B) A+B, #define g(A,B) f(A,B)/f(A,B), int x=5; h(x, x++);" → Expand step by step, watch side effects!
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Storage Classes (register, static, auto, extern)Must Know
register: CPU register, CANNOT use & (no address!). static: retains value between calls. auto: default local. extern: defined in another file.
BITS PYQs: "Can't use & operator?" → register. "Maintains value between calls?" → static int
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Union vs Structure (sizeof)Must Know
Union: all members share memory, size = LARGEST member. Struct: sequential, size = sum + padding.
BITS PYQ: "union{int a;char c;double d;} with int=4,char=2,double=5. Size?" → 5 bytes (largest member)
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fork() System CallMust Know
Creates child process (copy of parent). Returns 0 to child, PID to parent. Variables are COPIED - child's changes don't affect parent.
BITS PYQ: "int x=5; fork(); if(pid!=0) print x; else x++;" → Parent prints 5 (child modifies its OWN copy)
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File I/O FunctionsImportant
fflush: flush buffer to file. fseek: move pointer (random access). fgets: read line. ftell: current position. fforword: DOES NOT EXIST.
BITS PYQs: "Not standard C function?" → fforword(). "Diff fflush vs fseek?", "How is fgets used?"
OOP & Software Engineering
High - ~10-12 Questions
BITS PYQs: 13 Questions
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Testing MethodsMust Know
White/Clear box: see internals. Black box: only I/O. "Color box" does NOT exist. Beta testing: done by CUSTOMERS.
BITS PYQs: "Not a testing method?" → Color box. "Who does beta testing?" → Customers
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Design Patterns & ArchitectureMust Know
Patterns: Factory, Singleton, Observer, Strategy. Architectures: Pipes&Filters, Microkernel, Layered. Facade is a PATTERN not architecture.
BITS PYQs: "Identify pattern for use case", "Not a software architecture?" → Facade (it's a design pattern)
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SDLC Models & COCOMOImportant
Waterfall: NOT for changing requirements. COCOMO II: Algorithmic approach. UML Sequence: shows class lifecycle.
BITS PYQs: "Waterfall bad for?" → Accommodating changes. "COCOMO II approach?" → Algorithmic
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OOP Concepts & Design PrinciplesGood to Know
Good design = High Cohesion + Low Coupling. Inheritance: IS-A. Composition: HAS-A. Polymorphism: same interface, different behavior.
BITS PYQs: "Good software design features?" → High cohesion, low coupling. Know inheritance, object, class definitions.
05 12-Day Study Plan
Prioritized by frequency in BITS PYQs + GATE weight. Adjust based on your strengths. Do PYQs after each topic.
Days 1-3: Highest Impact
- Data Structures (AVL, BST, Hashing, Stack/Queue)
- OS (Page Replacement, Scheduling, Deadlock, Sync)
- Probability (Poisson, Binomial, Bayes, E(X))
- C Programming [SS only] (Pointers, Macros, fork, Union)
Days 4-6: Core Subjects
- Algorithms (Complexity, Sorting, Graph Algorithms)
- Computer Networks (Subnetting, TCP/UDP, HTTP)
- Linear Algebra (Eigenvalues, Rank, Systems)
- Complex Variables (Residues, Roots, i^i)
Days 7-9: Complete Coverage
- DBMS (Normalization, SQL, ER, 2PL)
- Digital Electronics (K-maps, MUX, Flip-Flops)
- COA (Pipeline, Cache, Address Space)
- TOC (DFA, CFG closure, Undecidability)
Days 10-12: Finish + Revise
- Compiler (Phases, Grammar, Parsing basics)
- Discrete Math (Counting, Functions, Logic)
- Calculus (Maxima, Series, Polar)
- English & Reasoning (Prepositions, RC, Series)
- OOP/SE [SS only] (Testing, Patterns, SDLC)
- REVISE ALL BITS PYQs!
✅
Final Exam Tips:
• BITS HD questions are easier than GATE — focus on concept clarity, not speed.
• -1 marking: If unsure between 2 options → attempt. If no idea → SKIP.
• Time per question: Test I = 1.5 min/Q, Test II = 1.5 min/Q, SS = 1.2 min/Q.
• Many BITS PYQs repeat in SPIRIT (same concept, different numbers). Do ALL PYQs twice.
• For CS: expected cutoff ~120-150/300 (Test I + Test II). For SS: ~100-130/240.