Computer Science Previous Year Questions (page 3)

Explanation

The C2B model, also called a reverse auction or demand collection model, enables buyers to name their own (often binding) price for a specific good or service. The website collects the bids and offers them to participating sellers. C2C is consumer to consumer, and B2B and B2G have nothing to do with consumer price setting.

Explanation

Inventory and data mining have nothing to do with price. Economic Order Quantity (EOQ) is the order quantity that minimizes total holding and ordering costs. The demand-sensitive pricing model brings prices down as more customers buy the product at once.

Explanation

The umbrella activities in a software development life cycle process include the following: software project management, formal technical reviews, software quality assurance and software configuration management. Umbrella activities occur throughout the software process and focus primarily on project management, tracking and control.

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Effective software metrics should be simple, computable, consistent, objective and consistent in the use of units and dimensions. They should not be programming language dependent, otherwise they cannot measure software consistently.

Explanation

Cyclomatic complexity measures the logical complexity of a program (the number of independent paths). It can be computed as: (1) the number of regions of the flow graph; (2) V(G) = E – N + 2, where E is the number of edges and N the number of nodes; (3) V(G) = P + 1, where P is the number of predicate nodes in the flow graph G.

Explanation

These process areas belong to maturity level 3 (Defined), which includes Requirements Development, Organizational Process Focus (OPF), Organizational Training (OT), Integrated Project Management (IPM) and Risk Management (RSKM).

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Software architecture is the set of significant decisions about the organization of a software system: the structural elements and their interfaces, their behaviour and collaboration, and their composition into larger subsystems.

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A computer based information system is needed because of the growing size of organizations which need to process large volumes of data, and such data must support timely and accurate decisions. So III and IV are true.

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In increasing order of access speed: Magnetic tapes < Optical disks < Magnetic (hard) disks < Electronic disks (flash/SSD) < Main memory < Cache < Registers.

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Internal interrupts occur due to internal errors (like division by zero) and external interrupts come from hardware. Software interrupts are the most appropriate way to switch from user mode to supervisor (kernel) mode.

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For any comparison-based sort the decision tree has at least n! leaves, so its height is at least lg(n!) = Ω(n lg n).

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Dijkstra's algorithm for the single-source shortest-paths problem is a greedy algorithm, and the Floyd-Warshall algorithm for all-pairs shortest paths is a dynamic programming algorithm.

Explanation

To show CLIQUE is NP-hard, a known NP-complete problem must be reduced to CLIQUE (e.g. 3-CNF-SAT ≤ₚ CLIQUE), not the other way round. Reducing CLIQUE to 3-CNF-SAT, VERTEX_COVER or SUBSET_SUM only shows CLIQUE is no harder than them. So the answer is None of the above.

Explanation

Autoboxing is the automatic conversion that the Java compiler makes from primitive types to their corresponding object wrapper classes.

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S1 is true: in call-by-value, anything passed into a function is unchanged in the caller's scope when the function returns. S2 is true: in call-by-reference the function receives an implicit reference to the argument variable. S3 is false, because in call-by-reference the caller always sees the modified value of the argument.

Explanation

Synchronization is the capability to control the access of multiple threads to shared resources. Without it, one Java thread could modify a shared variable while another thread is using or updating the same variable; synchronized methods prevent this.

Explanation

In the applet life cycle, init() is called first, followed by start(), paint(), stop() and destroy().

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Check-pointing saves a snapshot of the system state periodically, so that after a failure recovery can restart from the last checkpoint; this limits the volume of log information that has to be processed.

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Windows Vista's built-in disk management (Logical Disk Manager) supports shrinking and expanding volumes.

Explanation

Every binary relation (a relation with only 2 attributes) is always in BCNF: if both attributes form the key it is in BCNF, and if one attribute is the key the other is determined by it. So statement (a) is false.

Explanation

HDLC (High-level Data Link Control) is a bit-oriented, code-transparent, synchronous data link layer protocol from ISO. It can be used for point-to-point and point-to-multipoint links.

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Two phase locking is a pessimistic protocol (it assumes conflicts will happen) because it applies locks. Time stamping is an optimistic protocol because it uses no locking and handles conflicts later. So II and III are correct.

Explanation

A JavaScript program can define the behaviour of document elements by registering appropriate event handlers.

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Dithering approximates halftones without reducing spatial resolution. The dither matrix is treated like a floor tile that is repeatedly positioned one copy next to another to cover the entire image.

Explanation

All three categories refer to animation languages: linear-list notations (e.g. 'B rotate palm'), general-purpose languages (e.g. ASAS), and graphical languages. So the answer is None of the above.

Explanation

The pumping lemma for regular languages can only be used to prove that a language is not regular. Both L₁ (which needs to compare n and k) and L₂ (which needs to compare n and m) require unbounded counting, so neither is regular.

Explanation

S₁: Boolean expressions and logic networks correspond to labeled acyclic digraphs. S₂: Minimal expressions do not always give the simplest network. S₃: Greedy K-map grouping may not give an optimal expression. So S₁, S₂ and S₃ are all correct.

Explanation

For a full adder, S = A ⊕ B ⊕ Cᵢₙ and Cₒᵤₜ = A·B + Cᵢₙ·(A ⊕ B). (a) A = 1, B = 0, Cᵢₙ = 0: S = 1 ⊕ 0 ⊕ 0 = 1, Cₒᵤₜ = 1·0 + 0·(1 ⊕ 0) = 0. (b) A = 0, B = 1, Cᵢₙ = 1: S = 0 ⊕ 1 ⊕ 1 = 0, Cₒᵤₜ = 0·1 + 1·(0 ⊕ 1) = 1. So S = 1, C₀ = 0 and S = 0, C₀ = 1.

Explanation

S₁: (c ∧ b) → r S₂: ¬b → ¬p Conclusion: (¬r ∧ p) → ¬c So: if (c ∧ b) → r and ¬b → ¬p, then (¬r ∧ p) → ¬c.

Explanation

(a) Contrapositive: negate both hypothesis and conclusion and interchange them: (p → q) ⇔ (¬q → ¬p). (b) Exportation is a valid rule of replacement: ((p ∧ q) → r) ⇔ (p → (q → r)). (c) Reductio ad absurdum: (p → q) ⇔ [(p ∧ ¬q) → 0]. (d) Equivalence (biconditional): (p ↔ q) ⇔ (p → q) ∧ (q → p). So a-(i), b-(ii), c-(iii), d-(iv).

Explanation

The proposition is "if x² ≥ 25 then x ≥ 6", but the proof assumes x ≥ 6 and derives x² ≥ 25. So the proof starts by assuming what is to be shown and actually proves the converse; the proof is not correct. Statements (1) and (2) are correct, statement (3) is not.

Explanation

Message passing interface (MPI) is a standardized and portable message passing system. • It can run on any hardware platform. It is portable, efficient, flexible. • It has become a de facto standard for communication among memory system. • MPI – Comm. – Size returns the total number of MPI processes in specified communication. So answer is (c)

Explanation

Translator which performs macro calls expansion is called macro pre-processors

Explanation

Take the first node in preorder traversal a will be the root. Now we construct the binary tree Therefore, postorder is - debfgca

Explanation

Level order traversal is similar to breadth first search, whereas preorder traversal is similar to depth first search. So the answer is (a).

Explanation

The complexity is commonly estimated by counting the number of elementary operations performed by the algorithm, where an elementary operation takes a fixed amount of time to perform. Thus the amount of time taken and the number of elementary operations performed by the algorithm differ by at most a constant factor.

Explanation

Linear search runs in at worst linear time and make at most n comparisons, where n is the length of the list. If each element is equally likely to be searched then the linear search has an average case of (n/2) comparisons, but the average case can be affected if the search probability for each element vary.

Explanation

Radix sort because it sorts in integers in range 0 … (n² – 1) in O(n) time using base-n representation.

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Using Kruskal's algorithm: take 10 (1–6), 12 (3–4), 14 (2–7), 16 (2–3); skip 18 (4–7, cycle); take 22 (4–5); skip 24 (5–7, cycle); take 25 (5–6). Total = 10 + 12 + 14 + 16 + 22 + 25 = 99, which is option (b).

Explanation

Relational operators > and >= have higher precedence than ==, so the expression is (--x + j) == ((x > n) >= m). --x makes x = 6.5, so LHS = 6.5 + (–1.0) = 5.5. RHS: (6.5 > 1.0) = 1, then (1 >= 2.0) = 0. 5.5 == 0 is false, so the value is 0.

Explanation

S occupies addresses 1000 to 1008: A B C D E F G H \0. S[3] is 'D', and *(&S[3]) is 'D' itself, so %c prints D. S + 4 skips 4 characters, so %s prints "EFGH". %u prints the base address of S, 1000. Final output: DEFGH1000.

Explanation

Reference string 0 1 7 2 3 2 7 1 0 3 with 4 frames (LRU): 0, 1, 7, 2 are faults (4); 3 replaces 0 (5); 2, 7, 1 are hits; 0 replaces 3 (6); 3 replaces 2 (7). Total page faults = 7.

Explanation

Reading of two process won't create any problem, So answer is (c)

Explanation

By Amdahl's law, the serial part (1 – P) cannot be sped up while the parallel part P is divided among N processors, so the maximum speed-up is 1 / [(1 – P) + P/N].

Explanation

SSTF from cylinder 24: 24 → 26 (2) → 12 (14) → 8 (4) → 4 (4) → 42 (38) → 50 (8). Total distance = 70 cylinders. Seek time = 70 × 6 msec = 420 msec = 0.42 sec.

Explanation

The Unix Kernel maintains two key data structures related to processes, the process table and the user structure. In user structure there is no place for scheduling parameter process table store the information of all running process. The process table contains process ID's, memory usage of the process, what are file descriptor used in the process.

Explanation

Traditional file system has all mentioned drawbacks. Database applications built by using tables are used to overcome them. eg : Normalization and integrity constraints reduces redundancy & inconsistency. Select * from table provide easy access to data references, joins etc removes data is action primary & foreign key along with check predicates solves integrity problem

Explanation

Every weak entity must be associated with an identifying entity i.e. the weak entity set is said to be existence dependent on the identifying set. The identifying entity set is said to own the weak entity set that it identifies. It is also called owner entity set.

Explanation

If you drop child table first, the foreign key will be dropped as well. If you attempt to drop percent table first you will get an "could not drop object "a" because it is referenced by a foreign key constraint error, Drop table can not be used to drop a table reference by a foreign key constraint. The referencing foreign key constraint or the referencing table must be dropped.