Computer Science Previous Year Questions (page 2)

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A DBMS supports many users at once, so 'single-user access only' is not a feature.

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Databases manipulate and secure data; analysing code is not a database function.

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Data that describes other data is called metadata.

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A DBMS sits between the database applications (users' programs) and the stored database.

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A superkey is any set of attributes that together uniquely identify a record.

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'DELETE FROM teaches;' removes all rows (values) of the relation; the other forms are wrong or remove different things.

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In the SQL hierarchy, the top level is made of catalogs, each of which can contain schemas.

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In SQL Server the db_accessadmin role can add or remove user IDs (access) for a database.

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Folders inside filing cabinets form a tree of parent and child containers, which is the hierarchical model.

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The HAVING clause filters groups after GROUP BY and may use aggregate functions.

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Only III (process organization) is not a DBMS utility, but none of the options A-C lists exactly that, so the answer is None of the above.

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Third normal form (3NF) is generally considered adequate for a normal relational design.

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Duplicate storage wastes space and, if one copy is changed, makes the copies inconsistent; option A states both.

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RAW stores unstructured binary data in a column; Numeric and VARCHAR hold structured numbers and text.

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XNOR gives output 1 when both inputs are equal.

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Data flows only from the keyboard to the computer, which is simplex transmission.

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X + Y + XY = X + Y, and (X + Y)(X + Z) = X + YZ by the distributive law.

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The dual is formed by swapping 0 and 1 and also swapping + with '.', without complementing the variables.

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Radio waves, microwaves and infrared are all wireless media, so more than one option is correct.

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A switched network sends frames only to the intended port, which makes packet sniffing much harder than on a shared medium.

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In time-division multiplexing each slot is further divided into frames.

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TCP is connection-oriented, sets up a connection with a three-way handshake and takes data from the application as one stream, so A, B and C all hold.

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The endpoint of a communication flow between processes over a network is a socket.

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Optical fibre carries data as light and offers the highest speed and bandwidth of these media.

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NAND and NOR are both universal gates, so any digital circuit can be built by repeatedly using either one. AND alone is not universal.

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None of the statements fit digital circuits: they use discrete (0/1) signals rather than analog or continuous voltage levels, and they are well suited to high-speed operation.

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Computers, mobile phones and digital cameras all process information as digital (binary) signals, so more than one option is correct.

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A truth table with n inputs has 2ⁿ rows, so 4 inputs give 2⁴ = 16 rows.

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A negative (low) level-triggered flip-flop responds to its inputs and can change state only while the clock is at its low (0) level.

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Bitwise AND gives 1 only where both bits are 1: 1010 AND 1100 = 1000.

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A half adder adds two bits and outputs a Sum (A XOR B) and a Carry (A AND B). Difference and Borrow are the outputs of a half subtractor.

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PROM, EPROM and MROM (mask ROM) are all types of read-only memory, so more than one option is correct.

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PLA stands for Programmable Logic Array, a device with a programmable AND array followed by a programmable OR array.

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An 8-to-1 multiplexer needs n select lines where 2ⁿ = 8, so n = 3.

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1234 = 4×256 + 13×16 + 2, so it is 4D2 in hex. In octal, 2×512 + 3×64 + 2×8 + 2 = 1234 gives 2322, and binary 100 1101 0010 is 10011010010.

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Booth's algorithm multiplies signed binary numbers in two's complement form.

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Hamming code, CRC and checksum are all codes for detecting errors (Hamming can also correct them), so more than one option is correct.

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A BCD digit uses 4 bits but only codes 0 to 9, so its maximum value is 9. That is not among the options; any sum above 9 needs +6 correction.

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1011 = 11, and .1101 = 0.5 + 0.25 + 0 + 0.0625 = 0.8125, so the value is 11.8125. None of the listed values matches.

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De Morgan's theorems, (AB)' = A' + B' and (A + B)' = A'B', are used to simplify Boolean expressions and to turn circuits into NAND/NOR-only forms, so both A and B are correct.

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A don't-care condition marks an input combination whose output value does not matter, so it can be taken as 0 or 1 to simplify a K-map.

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Stack, queue and array are all linear data structures. Trees and graphs are non-linear, and neither is listed.

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A hash table supports search, insertion and deletion in O(1) average time. A stack or queue only gives access at its ends.

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In a BST, keys smaller than a node go in its left subtree and larger keys in its right subtree.

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Official BPSC final answer key: (E). The expression leaves an unused operand “8”, so no listed value is correct.

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In a height-balanced (AVL) binary tree, the heights of the left and right subtrees of every node differ by at most 1.

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The fragment int a[] = {1,2,3,} *p; is missing a separator before *p, so it will not compile. It gives neither a junk value, 3, nor a runtime error.

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The front element d must stay in place. Delete a, b and c (3 deletions) and add them back as c, b, a (3 additions), giving d, c, b, a.

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Binary search halves the search range at each step, so its order is O(log n). That is not among N, N log n or N².

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Root 15. The left subtree from 10, 12, 11 is 10 with right child 12, whose left child is 11. The right subtree is 20 with left child 18, whose children are 16 and 19. Postorder: 11, 12, 10, 16, 19, 18, 20, 15.