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

Explanation

For 0 ≤ t ≤ 1 the point (cos πt/2, sin πt/2) traces a quarter of the unit circle from (1, 0) to (0, 1). Rotating it about the X axis gives a hemisphere of radius 1, whose curved surface area is 2πr² = 2π.

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The only singularity, z = −1 (a pole of order 4), lies inside |z| = 3. By Cauchy's formula the integral is 2πi·f'''(−1)/3! with f = e^(2z), f''' = 8e^(2z), giving 2πi·8e⁻²/6 = (8/3)πi e⁻².

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Field reports are written after observing or surveying conditions on site (inspections, surveys, investigations), so they fall under survey reports. Project, sales and annual reports are progress or periodic reports.

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Femto means 10⁻¹⁵. Pico is 10⁻¹², nano is 10⁻⁹ and atto is 10⁻¹⁸.

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ENIAC (1946, Eckert and Mauchly) stands for Electronic Numerical Integrator and Computer.

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1715 ÷ 12 = 142 remainder 11 (B); 142 ÷ 12 = 11 remainder 10 (A); 11 = B. Reading the remainders upward gives (BAB)₁₂. Check: 11×144 + 10×12 + 11 = 1715.

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Software evolution covers changes in software architecture (structure and design of systems over time) as well as in programming languages and paradigms used to build them, so both are aspects of evolution.

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An operating system manages processes (creation, scheduling), memory (allocation, paging) and security/protection of resources, so all three are OS functions.

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Indices i, i+1, ..., j contain j − i + 1 elements. For example, indices 0 to 9 give 10 elements.

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Binary search keeps narrowing Beg..End; when Beg passes End (End < Beg) the search range is empty, so the element is not present.

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A C identifier may contain letters, digits and underscores, and may begin with a letter or an underscore (but not a digit). Both statements are true.

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A wide-character literal is written with the prefix L, for example L'a', and has type wchar_t.

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Average cases: binary search O(log n) < linear search O(n) < quick sort O(n log n) < selection sort O(n²).

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In C the result of % takes the sign of the dividend: 7 % −3 = 1 and −7 % 3 = −1. The two printf calls print 1 and −1.

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The preprocessor stage replaces #include lines with the file contents and expands macros; the key also counts handling of escape sequences in this preprocessing step, so all three are taken as correct.

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Scanning left to right: M N O + * gives M*(N+O); then P / gives (M*(N+O))/P; Q R S T / + * gives Q*(R+S/T); the final − joins them: ((M*(N+O))/P) − (Q*(R+(S/T))).

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71 is the root; 56 and 48 go left; 96 goes right; 76 becomes the left child of 96; 82 goes right of 76 (level 4); 98 is the right child of 96. So 82 is at the deepest level.

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I: 4×343 + 0×49 + 5×7 + 2 = 1372 + 35 + 2 = 1409. II: 1715 = 11×144 + 10×12 + 11 = (BAB)₁₂. Both are correct.

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ANSI X12 is the standard for electronic data interchange (EDI) of business documents. X.75 links packet networks, and XON is a flow-control character.

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EBCDIC is the Extended Binary Coded Decimal Interchange Code, an 8-bit character code used on IBM mainframes.

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E = 69 = 1000101, X = 88 = 1011000, A = 65 = 1000001, M = 77 = 1001101. Joining the four 7-bit codes gives 1000101 1011000 1000001 1001101, which is option B.

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A compiler translates the whole source program into object (machine) code. A linker combines object files, and a loader places the program in memory.

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Complementary subtraction does subtraction by adding the complement (1's, 2's, 9's or 10's) of the subtrahend, so subtraction becomes addition.

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In series the resistances add: 3 + 3 + 3 = 9 ohm. The keyed value is this equivalent resistance.

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The output is 1 only when both inputs are 1, which is the AND function.

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E(E + F) = E, and E absorbs DE. D(E + F) = DE + DF, and DE is again absorbed by E. What remains is E + DF.

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A half subtractor computes A − B: difference = A ⊕ B and borrow = A'B, since a borrow is needed only when A = 0 and B = 1.

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A monostable multivibrator has one stable state and one quasi-stable state: a trigger moves it to the quasi-stable state for a fixed time, after which it returns.

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A demultiplexer with m select lines routes the input to one of 2^m outputs, so n = 2^m (e.g. 1-to-8 DEMUX has 3 select lines).

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B ⊕ B = 0, because XOR gives 1 only when its inputs differ, and here both inputs are always equal.

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ISAM is Indexed Sequential Access Method: records are stored sequentially by key and an index allows direct access.

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Note from the source book: a primary index on a sequentially ordered file is in fact a sparse index (option d), but the official key (as per the Board) is (b) Clustering index.

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A deductive database model derives new facts from stored facts using rules (logical inference), so it is also called the inference model.

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The data catalog (data dictionary) is a system database holding metadata, i.e. the description of tables, columns, constraints and other database objects.

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A 2NF relation must be in 1NF (I is correct). Statement II says non-key attributes are "independent" of the primary key, but 2NF requires them to be fully functionally dependent on it, so II is wrong.

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By De Morgan's law the complement of a sum of products is a product of sums with each literal complemented: (AB)' = A' + B', (C'D)' = C + D', (B'D)' = B + D'. So F' = (A' + B')(C + D')(B + D').

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With columns CD = 00, 01, 11, 10: row AB=00 holds m0, m1, m3, m2 → 1 1 _ 1; row 01 holds m4, m5, m7, m6 → only m6; row 11 is empty; row 10 holds m8, m9, m11, m10 → 1 1 _ 1. This matches option A.

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A flip-flop is a bistable circuit with two stable states, so it stores exactly one bit (0 or 1).

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In Chrome on Windows, Ctrl + Shift + I (or F12) opens Developer Tools.

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The journal records transactions in date order (book of original entry, chronological), while the ledger classifies them account-wise (analytical record). Both statements are correct.

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Depreciation can be charged by the straight line method (fixed amount each year) or the written down value method (fixed rate on the reducing balance). Both are standard methods.

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Equivalence partitioning divides input data into valid and invalid classes and tests one value from each, using only the specification, so it is a black box technique.

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A DFD is also called a bubble chart because processes are drawn as circles (bubbles).

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In the spiral model (Boehm), software is developed in a series of evolutionary or incremental releases, one per loop of the spiral, with risk analysis in each cycle.

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CASE stands for Computer Aided Software Engineering: software tools that support analysis, design, coding and testing.

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Boehm's definitions: verification asks "Are we building the product right?" (conforms to specification) and validation asks "Are we building the right product?" (meets user needs).

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A feasibility study checks whether a project is worth doing, including financial (economic) feasibility and technical feasibility, along with operational and schedule aspects.

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McCabe's cyclomatic complexity for a connected control flow graph is V(G) = E − N + 2 (or number of decisions + 1).

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An applet is a small Java program embedded in an HTML page and run by a Java-enabled browser.

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After break the control leaves the switch, and no case label precedes a4 = 10000;, so that statement can never be reached. a1, a2 and a3 run for cases 1 and 2 (case 1 falls through).

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Spooling (Simultaneous Peripheral Operations On-Line) stores output on disk and sends it to the slow printer later, so the CPU need not wait for the printer.

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Disabling (masking) an interrupt means setting a mask bit so the CPU ignores that interrupt until it is unmasked.

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Faults for 4, 7, 6 (3). Page 1: evict 4 (never used again), fault 4. 7, 6, 1 hit. Page 2: evict 6 or 1 (never used again), fault 5. 7 and 2 hit. Total 5 page faults.

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The kernel is the core of the OS that stays resident in main memory and directly manages CPU, memory and devices.

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Privileged instructions (I/O, changing the timer, disabling interrupts, etc.) can run only in kernel mode; attempting them in user mode causes a trap.

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Seek time is the time to move the read/write head to the required track. Latency (rotational delay) is the wait for the sector to rotate under the head.

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The OS keeps a Thread Control Block (TCB) per thread, storing its thread ID, register set, stack pointer, state and priority. A PCB stores information for a whole process.

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Monotonic preferences mean more of a good is better, so to keep utility constant a consumer must give up some of one good to get more of the other, which makes indifference curves slope downward.

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Moral suasion (persuasion and advice to banks) is a qualitative or selective tool. CRR, bank rate and open market operations are quantitative tools that act on the total money supply.

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Half duplex allows communication in both directions but only one direction at a time (e.g. walkie-talkie). Full duplex allows both at once; simplex is one-way only.

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DVMRP is the Distance Vector Multicast Routing Protocol, used for routing multicast traffic.

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The carrier is sent for bit 1 and switched off for bit 0. This is on-off keying, a form of amplitude shift keying, i.e. amplitude modulation of the binary signal.

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Attenuation is the loss of signal energy (strength) as the signal travels through the medium, which is why repeaters or amplifiers are needed.

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Systems where many users share one channel and their transmissions can collide are called contention systems (e.g. ALOHA, CSMA).

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Repeater works at the physical layer (IV), bridge at the data link layer (III), router at the network layer (I) and gateway at the transport layer or above (II).

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The Common Language Runtime (CLR) is the .NET virtual machine: it loads and runs code, and handles JIT compilation, memory management and security.

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Links (hard links and symbolic links) let the same file or directory appear at multiple places in the Linux directory tree.

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Delivery arrangements depend on the size, nature and urgency of the goods, but not on their cost, so cost of products is the answer.

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Only II is correct: certificates rely on public key cryptography. A certificate does include the issuing CA's name (I false), and certificates come in various key strengths, not only 128-bit (III false).

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A max-heap must be a complete binary tree with every parent ≥ its children. Option B satisfies both. A and C are not complete trees, and in D the node 50 has a larger child 80.

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LL and RR imbalances are fixed by one rotation (single rotations). LR and RL need two rotations, so they are double rotations.

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A red-black tree with n internal nodes has height at most 2log₂(n + 1), since the black height is at least half the height.

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20 goes to the right of 18, making 23 unbalanced (left height 2, right 0) with a left-right pattern. An LR double rotation makes 20 the subtree root with 18 and 23 as children, as in option B.

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The BST is 38 with left subtree 14 (8, and 23 with left child 18 whose right child is 20) and right subtree 56 (45, and 82 with left child 70). Postorder: 8, 20, 18, 23, 14, 45, 70, 82, 56, 38.

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A knowledge engineer extracts knowledge from the human expert (specialist) and encodes it into the expert system's knowledge base, acting as the intermediary between them.

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In batch processing, transactions are collected and the database is updated later (I false), it is relatively cheap (II false), and reports are produced at scheduled intervals (III true).

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GPRS is General Packet Radio Service, a packet-switched data service on 2G/GSM networks.

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GSM architecture has three subsystems: Radio Subsystem (RSS), Network and Switching Subsystem (NSS) and Operation Subsystem (OSS). All three are parts of it.

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Persistence is how long a phosphor continues to emit light after the electron beam is removed (time for light to decay to one-tenth of its original intensity).

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CMY = (1, 1, 1) − RGB, so (1 − 0.2, 1 − 1, 1 − 0.5) = (0.8, 0, 0.5).

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Scaling multiplies coordinates: x' = 2x, y' = 4y. A(0, 0) stays (0, 0), B(3, 3) becomes (6, 12), C(2, 5) becomes (4, 20).

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A webmaster manages and maintains web servers and websites. A web designer creates layout and look, not the server.

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MPEG-1/2 Audio Layer III files use the .mp3 extension. .mp4 is an MPEG-4 container, mainly for video.

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The key treats a knowledge contract (agreement on who contributes, owns and shares knowledge) as a factor in building a KMS. The other options are false: a KMS is costly, evolving, and has strong human implications.

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The keyed answer says a meeting report should begin with precise background information about the organisation holding the meeting, before details of the speeches and participants.

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In a flowchart, a rectangle stands for a processing step. A diamond is a decision, a parallelogram is input/output and an oval is start/end.

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User documentation explains what the program does, its purpose, how to use it and what output to expect (II and III). Program formatting belongs to technical (programmer) documentation.

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With six values, median = mean of 3rd and 4th values. Taking x between 8 and 12, the ordered list is 5, 7, 8, x, 12, 17, so (8 + x)/2 = 10, giving x = 12.

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P(defective) = 0.25×0.05 + 0.35×0.04 + 0.40×0.02 = 0.0125 + 0.014 + 0.008 = 0.0345. By Bayes' theorem, P(Q | defective) = 0.014/0.0345 ≈ 0.41.

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In a teacher-centred approach the teacher controls learning, uses extrinsic motivation (praise, rewards, punishment), and students mainly listen passively and reproduce what was taught. Both are features.

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Real objects may be too big or too small, unsafe to bring (dangerous animals, chemicals) or too costly, so size, safety and cost are all reasons.

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Checking whether students already have a prerequisite skill (using an atlas) before teaching a topic is diagnostic assessment of their prior knowledge.

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Good written feedback starts with praise of what is done well, then points out errors, and asks the student to make corrections rather than simply writing the correct answer. Both points apply.

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Language learning starts with oral skills: in the LSRW order listening comes first, closely followed by speaking, before reading and writing. The key accepts both as the first step.

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Listening to and singing poems, and talking about pictures, both give children chances to listen and speak in class.

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Drama works as a language activity when children have freedom to express themselves and enjoy it, so both freedom and enjoyment are needed.

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Painters and sculptors both create visual images (visual arts), so both are included.

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Gender is a socio-cultural construct (correct). Sex is biological, not "systemic"; it is gender that is socially and systemically constructed, so statement II is not correct.

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KGBVs are residential upper primary schools for girls from disadvantaged groups. They provide hostel facilities, life skill training and extra or bridge coaching for slow learners, so all three are features.