Computer Science Previous Year Questions (page 19)

Explanation

Digitization samples the analog signal at fixed time intervals (sampling) and rounds each sample to a finite set of levels (quantization). Both are used.

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Data compression (lossless or lossy, e.g. ZIP, JPEG, MP3) reduces the size of multimedia files for storage and transmission.

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The carrier's frequency changes with the bit value (higher for 1, lower for 0) while the amplitude stays the same, which is frequency modulation (FSK).

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ARQ is an error-control protocol in which the sender waits for a positive acknowledgement (ACK) before sending the next frame and retransmits on timeout or NAK.

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Coaxial cable is guided (wired) media. Radio, microwave and light (infrared) transmission are unguided (wireless).

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WDMA is Wavelength Division Multiple Access, used in optical networks where each station is given its own wavelength.

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A hub works at the physical layer, a switch at the data link layer, a router at the network layer and a gateway up to the application layer.

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A URL (Uniform Resource Locator) gives the address and location of a resource on the internet, e.g. https://example.com/page.html.

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A protocol is a set of rules that governs how two computer systems communicate and exchange data.

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.NET programs are compiled to Intermediate Language (MSIL/CIL), a CPU-independent instruction set that the JIT compiler later turns into native code.

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In a Linux ls -l listing, 'c' marks a character special (device) file. 'b' marks block special files and 'd' marks directories.

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SSL works between the application layer and the transport (TCP) layer, not between the network and transport layers. So D is the incorrect characteristic.

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Mobile security is a major barrier to m-commerce, m-commerce lowers transaction costs through streamlined processes, and mobile coupons and tickets are m-commerce services. All three are correct.

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Double hashing, quadratic probing and chaining resolve collisions. Folding is a method of computing a hash function, not a collision resolution technique.

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Merge sort is stable: equal keys keep their original order. Selection, quick and heap sort are not stable in their usual forms.

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Post-order traversal visits the left subtree, then the right subtree, then the node (Left, Right, Node).

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After deleting 13, the left subtree of 14 is just node 1 (height 1). The right subtree 64 → 98 → 85 has height 3. BF = 1 − 3 = −2.

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Insert 350 at the end (position 10). Its parent 150 is smaller, so swap. The new parent 300 is smaller, so swap again. 400 is larger, so stop: 400, 350, 200, 100, 300, 160, 170, 80, 40, 150.

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LCS is solved by dynamic programming, Huffman coding by a greedy algorithm, quick sort by divide and conquer, and the simplex method is for linear programming.

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An MIS draws on internal and external databases for its reports. Knowledge engines belong to expert systems, and data entry and inquiry processing are transaction processing tasks.

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GSM stands for Global System for Mobile communication, the 2G digital cellular standard.

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DHCP (Dynamic Host Configuration Protocol) extends BOOTP. It adds automatic, leased assignment of IP addresses and other settings.

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The control grid sits between the cathode and the anodes. Its negative voltage controls how many electrons pass, which sets the beam intensity (brightness).

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Aspect ratio 3 : 2 = width : height, so height = 4 × 2/3 = 8/3 inch.

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2D viewing: build the world-coordinate scene from modeling coordinates (III), convert to viewing coordinates (II), map to normalized coordinates using the window-viewport mapping (IV), then map to device coordinates (I).

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Geolocation lets users share their location with websites they trust; in browsers this is the HTML5 Geolocation API, which first asks the user for permission.

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A mailto: URL (e.g. mailto:abc@example.com) opens the user's email client to send an email.

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The two-dimensional view of knowledge management combines strategy (how KM supports the organisation's goals) and content (the knowledge itself). The key takes both.

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A questionnaire can be sent to many people at once at low cost, so it is the most convenient method for a large group. Interviews and observation suit small groups.

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Algorithm efficiency is measured by time complexity (running time) and space complexity (memory used).

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A loop whose condition never becomes false runs endlessly and is called an infinite loop.

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An algorithm is a step-by-step procedure that is independent of any programming language (I and III). It is actually easy to debug, so II is false.

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For a single trial (Bernoulli), variance = p × q = 0.7 × 0.3 = 0.21.

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P(defective | red) = P(red and defective) / P(red) = 0.04 / 0.20 = 0.2.

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By Bayes' theorem, P(P | standard) = (0.6 × 0.8) / (0.6 × 0.8 + 0.4 × 0.9) = 0.48 / 0.84 = 4/7.

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By linear interpolation, y rises by (12 − 8)/(6 − 2) = 1 per unit of x, so y(5) = 8 + 3 × 1 = 11.

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Both statements correctly describe the subject-centred approach: the textbook is the only source, and students memorise facts by repetition. So neither is incorrect.

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Teachers and students commonly make graphs, number and alphabet cards, and theme-based flash cards as low-cost teaching-learning materials. All three apply.

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When students learn while judging their own or others' work, assessment itself becomes a learning process (assessment as learning).

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In assessment as learning, students monitor and reflect on their own learning, so it is controlled by the student, not the teacher.

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A lesson plan covers what to teach (content and objectives), whom to teach (the learners) and how to teach (methods and materials). All three are components.

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NCF 2005 calls multilingualism an integral part of India's linguistic heritage, and a society's culture and attitude toward languages decide whether it stays monolingual or multilingual. Both are correct.

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Too much water weakens clay and causes cracks in slabs, and children must keep clean and hygienic while working with it. Both precautions apply.

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All performing arts rest on exploring, expressing and listening (observing), so all three are basics.

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Discrimination ignores individual needs, merit and potential, while separate toilets for boys and girls meet genuine needs and are not discrimination. Both are correct.

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Article 15(3) lets the State make special provisions for women and children. Article 45 is about early childhood care and education.

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y = x² is increasing on [1, 6], so its minimum is at x = 1: y = 1.

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The divergence of a curl is always zero, ∇·(∇ × V) = 0, for any vector field with continuous second derivatives.

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tan(A+iB) + tan(A−iB) = 2x and tan(A+iB)·tan(A−iB) = x² + y², so tan 2A = 2x/(1 − x² − y²), i.e. x² + y² + 2x cot 2A = 1. Subtracting 2 gives −1.