DSSSB TGT Computer Science PYQ (Technical), 1 Aug 2021, Shift 3

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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.

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A nominal partner only lends his name to the firm. He neither invests capital nor takes part in management, but is still liable to outsiders.

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Diligence means a computer can work for long hours with the same accuracy, without tiredness or loss of concentration.

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Pico means 10⁻¹², so 1 picosecond = 10⁻¹² s. 10⁻⁹ is nano and 10⁻¹⁵ is femto.

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I: 1071 = 2×512 + 0×64 + 5×8 + 7 = (2057)₈, correct. II: (1AF)₁₆ = 256 + 160 + 15 = 431, not 413, so only I is correct.

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Base 7 uses digits 0-6, so the largest four-digit number is 6666 (7777 is invalid). The smallest four-digit base-8 number is 1000, not 1111. Neither statement is correct.

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A transistor is a semiconductor device used as an electronically controlled switch or amplifier, and is the basic element of digital circuits.

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A compiler is system software that translates a high-level language program into machine language (object code) as a whole.

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Binary search needs at most ⌊log₂n⌋ + 1 comparisons. 2¹³ = 8192 ≤ 12000 < 16384 = 2¹⁴, so ⌊log₂12000⌋ = 13 and the maximum is 14.

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In the worst case (reverse-sorted input) bubble sort makes n(n−1)/2 comparisons and swaps, so it is O(x²) with x elements.

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main() is called by the system, but its body is written by the programmer, so it is treated as a user-defined function, not a library (pre-defined) function.

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cgets() (from conio.h) reads a string from the console. puts() writes a string, and getche()/getchar() read single characters.

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62 is decimal, 062 is octal = 6×8 + 2 = 50, and 0x62 is hexadecimal = 6×16 + 2 = 98. With no separators, the output is 625098.

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Bubble sort makes one swap per inversion. In S O R T E D (order D < E < O < R < S < T), the inversions are S:4, O:2, R:2, T:2, E:1, totalling 11 interchanges.

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Right-left-node is the exact reverse of preorder (node-left-right). The preorder is A, B, C, D, E, F, G, H, I, J, K, so the new-order is K, J, I, H, G, F, E, D, C, B, A.

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j takes the values 1, 2, 4, ... while j ≤ n, so the loop condition is checked about log₂n + 1 times, which is the keyed answer. Strictly, the final failing test makes it ⌊log₂n⌋ + 2.

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A DBMS is software for creating, managing, maintaining and retrieving data stored in a database (e.g. MySQL, Oracle).

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A MAN covers a city by connecting many LANs, and it can carry both data and voice. Both statements are correct.

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A multiplexer combines many low-speed input lines into one high-speed line (shared channel). A demultiplexer does the reverse.

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Star and bus are network topologies (along with ring, mesh, tree). There is no "car topology", so only I and II are correct.

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The transmission modes are simplex, half duplex and full duplex. "Half simplex" does not exist, so I and III are correct.

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A dot-matrix printer forms characters by pins striking an inked ribbon against paper, so it is an impact printer. Inkjet, laser and thermal printers are non-impact.

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Speech recognition converts spoken words into computer input or text. Speaker recognition only identifies who is speaking.

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Coulomb's law: F = k·q₁q₂/r², so the force is directly proportional to the product of the charges and inversely proportional to the square of the distance.

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1 + A = 1, and (A + B)(A' + B) = B + AA' = B. So the expression simplifies to B.

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NOR-ing each input with itself gives A' and B' (2 gates). A third NOR gives (A' + B')' = AB. So 3 NOR gates are needed.

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The crossing must close if any one or more of the 4 tracks has a train, i.e. output 1 when at least one input is 1, which is the OR function.

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m0 (000) and m2 (010) group to A'C'. m5 (101) and m7 (111) group to AC. So f = A'C' + AC.

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An astable multivibrator is free running (no stable state), and a bistable multivibrator is the flip-flop. Both pairs are swapped, so neither is correct.

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Multiplexers can implement any logic function directly, which simplifies design, reduces the IC package count and removes the need to minimise the expression. All three are advantages.

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The first two factors are 1. (A + B + C)(A' + B' + C') is 0 only when A, B, C are all equal, which is what AB' + B'C + A'B + A'C + AC' + BC', i.e. option B, expresses.

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Key attributes of good information include accuracy, timeliness, relevance, completeness. Isolation is not an attribute of information.

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DASD stands for Direct Access Storage Device, such as a magnetic disk, where any record can be accessed directly.

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In a sequential file, inserting or deleting a record needs the whole file to be read and rewritten, and locating a record needs on average half the records to be scanned. Both are correct.

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Volatility measures how often records are added or deleted. Frequent additions and deletions mean high volatility.

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An entity is described by its attribute values. For example, a student entity is described by values of roll number, name and class.

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REAL, INTERVAL and TIMESTAMP are SQL data types. BASE is not an SQL data type.

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A truth table lists the output for every combination of binary inputs, giving the input-output relation of a gate in tabular form.

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Boolean algebra expresses the input-output relation of logic diagrams algebraically, which makes analysing and designing digital circuits easier. Both statements are correct.

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By De Morgan's theorem (x + y)' = x'·y', i.e. x'y'.

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A NOR gate can be drawn as an OR symbol with an output bubble, or, by De Morgan's law (A + B)' = A'B', as an AND symbol with bubbles on both inputs. Both represent NOR.

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A callback function is passed as an argument to another function and called back inside it, e.g. in setTimeout or event handlers.

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AJAX stands for Asynchronous JavaScript and XML: it updates parts of a page by exchanging data with the server in the background.

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A provision is a charge against profit made for a known liability or loss, while a reserve is an appropriation of profit kept aside for future needs. Both statements are correct.

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Permanent (real and personal) accounts are balanced and carried forward to the next period, while temporary (nominal) accounts are closed by transfer to the profit and loss account. Both are correct.

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White-box testing is also called glass-box (or clear-box) testing because the tester can see the internal code and logic.

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SQA stands for Software Quality Assurance: activities that make sure software processes and products meet quality standards.

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The spiral model develops software in a series of evolutionary releases, one per loop. A sequential (waterfall) model delivers the product only once at the end.

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Logical cohesion groups elements that do logically similar operations, such as all error handling or all data input routines. B describes functional cohesion and C procedural cohesion.

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Common coupling occurs when modules share the same global data area. Communicating through elementary data items is data coupling, and through composite data is stamp coupling.

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A Gantt chart can be derived automatically from a PERT chart, but a PERT chart cannot be derived from a Gantt chart because Gantt charts lack task dependencies. Both statements are false.

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The Java compiler (javac) translates source code into platform-independent bytecode (.class files), which the JVM then executes.

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Both are common errors: a semicolon after a method header ends the declaration, and in Java every method must be defined inside the class body braces. Neither statement is correct.

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x << 4 is 64 × 16 = 1024 = 0x400 (as int). Casting to byte keeps only the low 8 bits, 0x00, so y prints 0.

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In FIFO, increasing the number of frames can increase page faults for some reference strings (Belady's anomaly). Optimal and LRU are stack algorithms and do not suffer from it.

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Internal fragmentation is wasted space inside an allocated partition, when the partition is larger than the process placed in it.

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The unused 20K lies inside the partition already given to the process, so it is internal fragmentation.

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Total free memory (a + b) is enough, but it is not contiguous, so the process cannot be loaded. This is external fragmentation, which compaction can fix.

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Thrashing is the state in which the page fault rate is so high that the system spends most of its time swapping pages instead of executing; the key links the term to a high page-fault rate.

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Swapping out moves a process from main memory to disk (backing store). Swapping in brings it back into memory.

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1, 3, 4 fault (3); 4 and 3 hit; 2 fault (4); 1 hit; 7 fault (5) replacing 1; 5 fault (6) replacing 3; 6 fault (7) replacing 4. Total 7 page faults.

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CRR is the share of deposits banks must keep as cash with the RBI. SLR is kept by banks themselves in cash, gold or approved securities.

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National income can be measured by the product (value added) method, the income method and the expenditure method. All three measure the aggregate value of output.

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A price change affects consumer choice through the substitution effect (change in relative price) and the income effect (change in purchasing power). A cut in MSP is not one of these effects.

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The session layer (layer 5) handles dialogue control (who may send, and when) and token management, along with synchronisation.

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The network layer (layer 3) routes packets from source to destination across networks using logical (IP) addresses.

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Layers 1-3 are chained (they work hop-by-hop between adjacent devices), and layers 4-7 are end-to-end. The statements reverse this, so neither is true.

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The OSI layers are 1 Physical, 2 Data Link, 3 Network, 4 Transport, 5 Session, 6 Presentation, 7 Application. Layer five is the session layer.

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Native internet business models arose on the internet itself, such as library, freeware, information barter and digital product models. The subscription model is transplanted from the real world, so only I is correct.

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A sensible, easily guessed name and fresh attractive content (offers) increase visibility (I and II). III is false: social network icons do help e-visibility.

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In a BST, the value at N is greater than every value in its left subtree and less than (or equal to) every value in its right subtree. Both statements reverse this, so neither is correct.

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Each edge adds 2 to the total degree, so the sum of degrees is even (handshaking lemma), and hence the number of odd-degree vertices must also be even.

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A leaf node is removed by setting its parent's pointer to null (I correct). A node with two children is replaced by its inorder successor (or predecessor), not its preorder successor, so II is wrong.

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A Transaction Processing System is a type of information system that records routine business transactions. The other options are modes of data processing.

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In an expert system the machine asks the user questions (interaction from machine to user) and its knowledge domain is narrow. Producing information by analysing operational and external data describes MIS/DSS.

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Windows Mobile, Palm OS and Symbian are mobile operating systems. MANET (Mobile Ad hoc Network) is a type of wireless network, not an OS.

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Resolution is the maximum number of points that can be shown on a CRT without overlap, given as horizontal × vertical pixels.

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HTML has six heading levels, <h1> to <h6>.

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JavaScript is placed in a page with the <script> tag, either inline or through src.

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Knowledge management is the process of identifying, capturing, organising, storing and sharing knowledge within an organisation.

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A flow chart can organise notes visually to show the sequence and relation of ideas. Transition devices are linking words used in writing, not a method of organising notes.

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An oval (terminal symbol) marks the start and end of a flowchart. A diamond is for decisions and arrows show flow.

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Top-down design: analyse the problem (I), write the main module (III), write the remaining modules (V), connect the modules in order (IV), then revise and resequence (II).

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In a Poisson distribution, mean = variance = P, so the standard deviation is √P.

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P(no one solves) = (2/3)(3/4)(4/5) = 2/5. So P(solved) = 1 − 2/5 = 3/5 = 0.6.

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Lagrange's formula with two points: f(3) = 4·(3−5)/(1−5) + 6·(3−1)/(5−1) = 4×0.5 + 6×0.5 = 5.

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In a teacher-centred approach students mainly memorise what is taught and recall it from memory in tests, so both are key processes.

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Both statements are correct: TLMs help teachers manage multi-grade, multi-level classes, and they support self-learning. So neither statement is incorrect.

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A teacher must base decisions on sufficient evidence of learning and be sensitive to difficulties some students face in completing tasks. Both need attention.

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Formative assessment (during learning, to improve it) and summative assessment (at the end, to grade it) are both types of assessment.

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In principle a Hindi noun has 6 forms: 2 numbers (singular, plural) × 3 cases (direct, oblique, vocative). For example, laṛkā has laṛkā/laṛke (direct), laṛke/laṛkoṃ (oblique) and laṛke/laṛko (vocative).

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Sanskrit was the standard (elite) language of Brahmanic society, and Persian is the standard language of Iran. Both statements are correct, so neither is "not correct".

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Word and sentence choice depends on the context, the place or setting where we speak, and the theme or topic. All three are factors.

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Awareness of regional arts and crafts helps children recognise and promote traditional and contemporary art, and sensitises them to India's pluralistic cultural heritage. Both are correct.

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Gender discrimination can be direct (openly treating someone worse because of gender) or indirect (a neutral-looking rule that disadvantages one gender). Both forms exist.

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Empowered women take part in social change and in the development process, so both are indicators of women's empowerment.