Computer Science Previous Year Questions (page 32)

Explanation

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.

Explanation

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.

Explanation

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.

Explanation

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.

Explanation

TCP numbers every byte with sequence numbers and confirms receipt with acknowledgments. After recovery, the receiver can then detect and discard duplicate segments.

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UPDATE ... SET ... WHERE changes only the rows that match. Dividing by 1.1 gives the discounted bill, and the WHERE clause limits it to 'High privilege' accounts. MODIFY is not DML, and B has no WHERE.

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If the subquery returns no rows, the IN list is empty and the condition is false for every row, so no rows are deleted from Product and no error occurs.

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TRUNCATE removes all rows at once with little logging and no row-by-row triggers, so it is faster than DELETE. It keeps the table structure and is a DDL command.

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DROP TABLE removes the table's structure and all its data from the database permanently. TRUNCATE is the command that empties a table but keeps it.

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TCP sets up a connection with a three-way handshake (SYN, SYN-ACK, ACK). The two sides agree on initial sequence numbers before data is sent.