DSSSB TGT Computer Science PYQ (Technical), 7 Aug 2021, Shift 2

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In MS Word, Ctrl + J justifies the paragraph (aligns text to both margins). Ctrl + I is italic, Ctrl + S saves and Ctrl + Y redoes.

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Ctrl + T applies a hanging indent in MS Word (Ctrl + Shift + T removes it). Undo is Ctrl + Z, redo is Ctrl + Y and justify is Ctrl + J.

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Perverse software is software written to cause harm, i.e. malicious software (malware) such as viruses, worms and trojans.

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High-level languages are machine-independent, so programs are portable, and their readable English-like syntax makes errors easier to find and debug. Both are features.

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Cloud computing offers on-demand self-service, rapid scalability (elasticity) and a pay-per-use (measured service) billing model, so all three are key features.

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Apache HTTP Server is open-source software. PHP is also free and open source, but the official key accepts only Apache (Only II).

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Binary search needs a sorted list with direct (random) access to the middle element, which an array provides. A linked list has no direct access to the middle, so III is false.

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A matrix with a high proportion of zero entries is a sparse matrix; one with few zeros is a dense matrix.

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volatile is a C keyword (type qualifier). Automatic, Integer and Constant are not keywords; the C keywords are auto, int and const.

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Modifying val twice in one expression is undefined behaviour in C, but common compilers (e.g. GCC) apply both increments first, making val = 3, and then compute 3 * 3 = 9.

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A binary tree of height n has at most 1 + 2 + ... + 2ⁿ = 2ⁿ⁺¹ − 1 nodes (completely full) and at least n + 1 nodes (one node per level, a chain).

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^ binds tighter, so 3 ^ 4 is grouped first: 9 v (3 ^ 4) v 2. v is left associative, so it is (9 v (3 ^ 4)) v 2: root v with left child the inner v and right child 2.

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Full-duplex (duplex) mode lets both stations transmit at the same time. Half duplex allows both directions but only one at a time, and simplex is one direction only.

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BCD codes each decimal digit in 4 bits. 1000 has 4 digits, so 4 × 4 = 16 bits are needed.

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(100001)₂ = 33 and (110)₂ = 6. 33 ÷ 6 gives quotient 5 = (101)₂, remainder 3.

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EDVAC stands for Electronic Discrete Variable Automatic Computer, a stored-program machine designed by Eckert, Mauchly and von Neumann.

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Second-generation computers (about 1956-1963) used transistors in place of the vacuum tubes of the first generation. The third generation used ICs.

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The control unit directs and coordinates all parts of the computer, but it does no actual data processing itself; arithmetic and logic are done by the ALU. Both statements are true.

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In the Roman system a symbol has the same value wherever it appears (X is always 10), so it is non-positional. Decimal, octal and binary are positional.

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In series, resistances add: 4 + 4 = 8 ohm.

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The output is 0 only when both inputs are 0 and 1 otherwise, which is the OR function (A + B).

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In a half adder, sum = A ⊕ B and carry = A·B (AB), because a carry is produced only when both inputs are 1.

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In RTL the transistors are driven into saturation, so it is a saturated logic family. ECL keeps the transistors out of saturation, so it is non-saturated (and very fast). Both pairs are correct.

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m select lines can choose one of 2^m inputs, so a multiplexer with n inputs needs 2^m = n (e.g. 8 inputs need 3 select lines).

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With J and K tied together (J = K = T), the JK flip-flop holds when T = 0 and toggles when T = 1, which is a T flip-flop.

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A NAND gate with both inputs at A gives (A·A)' = A', so it acts as a NOT gate.

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Shadow paging is a recovery technique that needs no log: it keeps a shadow page table unchanged and a current page table for updates, and commits by switching tables.

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In an ER diagram an ellipse is an attribute and a diamond is a relationship. In crow's foot notation a circle with a bar means optional one, and a double bar means mandatory one.

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A timestamp is a unique value the DBMS gives each transaction when it starts, used to order transactions in timestamp-based concurrency control.

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The timestamp-ordering variants are total, partial and multiversion timestamp ordering. Multi-level timestamp ordering is not one of them.

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Data allocation is the process of deciding which sites of a distributed database will store each fragment or copy of the data.

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Data fragmentation splits a database (horizontally, vertically or mixed) into logical units called fragments, which can be stored at different sites.

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>= (greater than or equal to) is a comparison operator. + and / are arithmetic operators. = is also used for comparison in SQL, but the key takes >=.

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A POS expression is an AND of OR terms, which maps to a two-level NOR-NOR circuit. NOR is a universal gate, so POS is implemented with NOR gates.

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A D flip-flop copies its input on the clock edge: Q becomes 1 when D = 1 and goes to the 0 (reset) state when D = 0.

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R2' + 1 is the 2's complement of R2, so R1 + R2' + 1 adds R1 to the 2's complement of R2, which is R1 − R2, and stores it in R3.

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Micro-operations are classified into four types: register transfer, arithmetic, logic and shift micro-operations.

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One mode bit (the I bit) is enough: I = 0 for a direct address and I = 1 for an indirect address.

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A wireframe is a basic layout of a website that shows what content goes on each page and how the pages link (navigation between them). Both are true.

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MTTF means Mean Time To Failure, the average time a system runs before it fails. It is a common software reliability metric.

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The waterfall model is also called the linear sequential model (or classic life-cycle model) because its phases follow one after another.

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RAD (Rapid Application Development) is a high-speed version of the linear sequential model that gets fast delivery through component-based construction.

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Project estimation techniques are empirical, heuristic and analytical. Prototyping is a development model, not an estimation technique.

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A PERT chart is a network of boxes (or nodes) and arrows. The boxes are activities and the arrows show the dependencies between them, so both statements are true.

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In data dictionary notation, { } means iteration (repetition), ( ) means optional data and [ , ] means selection of one of the alternatives.

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Cohesion measures the functional strength of a module, i.e. how closely the elements inside one module work toward a single task. High cohesion is desirable.

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Java has no free-standing functions: every method must belong to a class, and member functions are called methods. Both are correct.

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Each test increments m and decrements k. The loop stops when m >= k, which first happens at m = 2000, k = 2000 (1000 iterations). So 2000 is printed.

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Rotational delay (latency) is the time spent waiting for the desired sector to rotate under the read/write head. Seek time is moving the head to the right track.

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A DMA controller moves data directly between I/O devices and main memory without passing each word through the CPU.

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The key fits a need of 3 drives per process: deadlock is impossible if n(3 − 1) + 1 ≤ 7, so n = 3. (If each needed only 2 drives as written, up to 6 processes would be safe.)

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Free memory = 500 − (100 + 130) = 270 KB. With compaction, all of it can be joined into one block, so any request up to 270 KB succeeds and the smallest request that can be denied is 271 KB.

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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.